Copy dev docs to DataDep docstring

and replace verbal cross-reference "below" by "in the documentation for
developers".

src/types.jl

@@ -32,53 +32,55 @@ DataDep(
     name::String,
     message::String,
     remote_path::Union{String,Vector{String}...},
-    [checksum::Union{String,Vector{String}...},]; # Optional, if not provided will generate
+    [hash::Union{String,Vector{String}...},]; # Optional, if not provided will generate
     # keyword args (Optional):
-    fetch_method=fetch_default # (remote_filepath, local_directory)->local_filepath
+    fetch_method=fetch_default # (remote_filepath, local_directory_path)->local_filepath
     post_fetch_method=identity # (local_filepath)->Any
 )
 ```
 
-#### Required Fields
+### Required Fields
 
- - *Name**: the name used to refer to this datadep, coresponds to a folder name where it will be stored
+ - `name`: the name used to refer to this datadep
+    - Corresponds to a folder name where the datatep will be stored.
     - It can have spaces or any other character that is allowed in a Windows filestring (which is a strict subset of the restriction for unix filenames).
- - *Message*: A message displayed to the user for they are asked if they want to downloaded it.
+ - `message`: a message displayed to the user for they are asked if they want to download it
     - This is normally used to give a link to the original source of the data, a paper to be cited etc.
- - *remote_path*: where to fetch the data from. Normally a string or strings) containing an URL
-    - This is usually a string, or a vector of strings (or a vector of vector... see [Recursive Structure](Recursive Structure) below)
-
-#### Optional Fields
- - *checksum* this is very flexible, it is used to check the files downloaded correctly
-    - By far the most common use is to just provide a SHA256 sum as a hex-string for the files
-    - If not provided, then a warning message with the  SHA256 sum is displayed. This is to help package devs work out the sum for their files without using an external tool.
-    - If you want to use a different hashing algorithm, then you can provide a tuple `(hashfun, targethex)`
-        - `hashfun` should be a function which takes an IOStream, and returns a `Vector{UInt8}`.
-          - Such as any of the functions from [SHA.jl](https://github.com/staticfloat/SHA.jl), eg `sha3_384`, `sha1_512`
-          - or `md5` from [MD5.jl](https://github.com/oxinabox/MD5.jl)
-  - If you want to use a different hashing algorithm, but don't know the sum, you can provide just the `hashfun` and a warning message will be displayed, giving the correct tuple of `(hashfun, targethex)` that should be added to the registration block.
-
-    - If you don't want to provide a checksum,  because your data can change pass in the type `Any` which will suppress the warning messages. (But see above warnings about "what if my data is dynamic")
-    - Can take a vector of checksums, being one for each file, or a single checksum in which case the per file hashes are `xor`ed to get the target hash. (See [Recursive Structure](Recursive Structure) below)
-
-
- -  `fetch_method=fetch_default` a function to run to download the files.
-    - Function should take 2 parameters (remotepath, local_directory), and must return a local filepath
-    - It is responsible for determining what the local filename should be
-    - Change this to change the transfer protocol, for example to use an auth'ed connection.
-    - Default `fetch_default` which fully supports HTTP, and has fallbacks to support any type which overloads `Base.basename` and `Base.download` (see [`fetch_base`](@ref))
-    - Can take a vector of methods, being one for each file, or a single method, in which case that method is used to download all of them. (See [Recursive Structure](Recursive Structure) below)
-    - Very few people will need to override this if they are just downloading public HTTP files.
-
- - `post_fetch_method` a function to run after the files have download
+ - `remote_path`: where to fetch the data from
+    - This is usually a string, or a vector of strings (or a vector of vectors... see [Recursive Structure](@ref) in the documentation for developers).
+
+### Optional Fields
+ - `hash`: used to check whether the files downloaded correctly
+    - By far the most common use is to just provide a SHA256 sum as a hex-string for the files.
+    - If not provided, then a warning message with the  SHA256 sum is displayed. This is to help package devs work out the sum for their files, without using an external tool. You can also calculate it using [Preupload Checking](@ref) in the documentation for developers.
+    - If you want to use a different hashing algorithm, then you can provide a tuple `(hashfun, targethex)`.
+      `hashfun` should be a function which takes an `IOStream`, and returns a `Vector{UInt8}`.
+      Such as any of the functions from [SHA.jl](https://github.com/staticfloat/SHA.jl), eg `sha3_384`, `sha1_512`
+      or `md5` from [MD5.jl](https://github.com/oxinabox/MD5.jl)
+    - If you want to use a different hashing algorithm, but don't know the sum, you can provide just the `hashfun` and a warning message will be displayed, giving the correct tuple of `(hashfun, targethex)` that should be added to the registration block.
+    - If you don't want to provide a checksum,  because your data can change pass in the type `Any` which will suppress the warning messages. (But see above warnings about "what if my data is dynamic").
+    - Can take a vector of checksums, being one for each file, or a single checksum in which case the per file hashes are `xor`ed to get the target hash. (See [Recursive Structure](@ref) in the documentation for developers).
+
+
+ -  `fetch_method=fetch_default`: a function to run to download the files
+    - Function should take 2 parameters `(remote_filepath, local_directorypath)`, and can must return the local filepath to the file downloaded.
+    - Default (`fetch_default`) can correctly handle strings containing HTTP[S] URLs, or any `remote_path` type which overloads `Base.basename` and `Base.download`, e.g. [`AWSS3.S3Path`](https://github.com/JuliaCloud/AWSS3.jl/).
+    - Can take a vector of methods, being one for each file, or a single method, in which case that method is used to download all of them. (See [Recursive Structure](@ref) in the documentation for developers).
+    - Overloading this lets you change things about how the download is done -- the transport protocol.
+    - The default is suitable for HTTP[/S], without auth. Modifying it can add authentication or an entirely different protocol (e.g. git, google drive etc).
+    - This function is also responsible to work out what the local file should be called (as this is protocol dependent).
+
+
+ - `post_fetch_method`: a function to run after the files have been downloaded
     - Should take the local filepath as its first and only argument. Can return anything.
     - Default is to do nothing.
-    - Can do what it wants from there, but most likes wants to extract the file into the data directory.
-    - towards this end DataDeps includes a command: `unpack` which will extract an compressed folder, deleting the original.
-    - It should be noted that it `post_fetch_method` runs from within the data directory
+    - Can do what it wants from there, but most likely wants to extract the file into the data directory.
+    - towards this end DataDeps.jl includes a command: `unpack` which will extract an compressed folder, deleting the original.
+    - It should be noted that `post_fetch_method` runs from within the data directory.
        - which means operations that just write to the current working directory (like `rm` or `mv` or ```run(`SOMECMD`))``` just work.
-       - You can call `cwd()` to get the the data directory for your own functions. (Or `dirname(local_filepath)`)
-    - Can take a vector of methods, being one for each file, or a single method, in which case that ame method is applied to all of the files. (See **Recursive Structure** in the README.md)
+       - You can call `cwd()` to get the the data directory for your own functions. (Or `dirname(local_filepath)`).
+    - Can take a vector of methods, being one for each file, or a single method, in which case that same method is applied to all of the files. (See [Recursive Structure](@ref) in the documentation for developers).
+    - You can check this as part of [Preupload Checking](@ref) in the documentation for developers.
 """
 function DataDep(name::String,
                  message::String,