Clean up project config rename deprecation warnings

[jtcohen6]

resolves #4276

• Create different deprecation warnings for each of source-paths and data-paths being renamed, so that both will display for users newly upgraded to v1
• Add a null handler to the global FILE_LOG when it's first instantiated, to prevent the un-configured FILE_LOG and STDOUT_LOG from both writing to stdout. This shouldn't have any functional impact, since the file logger isn't meant to be doing anything until it's configured, anyway

Also:

• Add \n\n to deprecation warning. ui.line_wrap_message() doesn't work perfectly with the new logging format just yet (it doesn't account for space taken up by timestamp + log level), so I'd prefer a cleaner break.
• In ui.line_wrap_message(), prevent textwrap.fill() from breaking on hyphens. This is awkward for PackageRedirectDeprecation, which includes hyphen-bearing package names.

Before:

$ dbt test
07:16:14 | [ info  ] | Running with dbt=1.0.0-rc1
07:16:14 | [ warn  ] | * Deprecation Warning: The `source-paths` config has been deprecated in favor of
`model-paths`. Please update your `dbt_project.yml` configuration to reflect
this change.
07:16:14 | [ warn  ] | * Deprecation Warning: The `source-paths` config has been deprecated in favor of
`model-paths`. Please update your `dbt_project.yml` configuration to reflect
this change.

After:

$ dbt test
06:50:56 | [ info  ] | Running with dbt=1.0.0-rc1
06:50:56 | [ warn  ] | * Deprecation Warning:
The `source-paths` config has been deprecated in favor of `model-paths`. Please
update your `dbt_project.yml` configuration to reflect this change.
06:50:56 | [ warn  ] | * Deprecation Warning:
The `data-paths` config has been deprecated in favor of `seed-paths`. Please
update your `dbt_project.yml` configuration to reflect this change.

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change

[nathaniel-may]

I noticed this when testing on one of my old projects and I found it annoying. Nice fix!

I do think a lot of this logic should actually live in the new events module, but I'm ok not doing that refactor right now. The bottom of the deprecation warnings looks like it drops out into events here, but I think most of the rest of this logic could live in there too. I've added it to the stretch goals list for phase 2. We can make a ticket for it if we don't get to it.

[jtcohen6]

Agreed - we treat deprecations sorta like exceptions, and we should eventually move all the deprecation / exception / warn_error logic into events. That can be TK