4813 allow duplicate files

[sekmiller]

What this PR does / why we need it:
This will allow users to upload multiple files with the same checksum value to a given dataset. On upload either via the interface or api the user will be warned that a duplicate file exists in the dataset (with the current path/label of the duplicate file.) At that point they can directly delete the newly uploaded file - if the upload is via the UI.

Which issue(s) this PR closes:
#4813 - allow files with the same MD5/checksum to exist in the same dataset

Closes #4813
Closes #6468

Special notes for your reviewer:
Really wanted to take a stick of dynamite to AddReplaceFileHelper, but ended up working with it as it exists. Also fixed an issue with the editFileMetadata api where if you weren't updating the file's label you'd get an duplicate file name error. This was causing a failure in the .testForceReplaceAndUpdate Test

Suggestions on how to test this:
various scenarios uploading a duplicate file including replace
document outlining upload use cases and expected messaging

Does this PR introduce a user interface change?:
Introduces a popup on upload of a duplicate file, which warns the user and allows them to immediately delete the newly uploaded file

Is there a release notes update needed for this change?:
We could note that duplicate files within a dataset are now allowed as a new feature

Additional documentation:

[coveralls]

Coverage decreased (-0.04%) to 19.562% when pulling 57ab613 on 4813-allow-duplicate-files into a6f580f on develop.

[sekmiller]

I updated the messaging based on discussion during the Design Meeting.

[kcondon]

So, I tested all the rules and used cases as best I could. I think they all work except on upload when paths are involved for duplicates that have not yet been saved.

1. Upload file2.txt twice, edit paths to be c,d. Cannot save, says duplicate filenames.
   This works if we upload a zip with dupe filenames in different paths.

[sekmiller]

I was able to upload duplicate files and edit their paths and successfully save them