Add the ability to deprecate Sources

[acoffman]

Sometimes people enter sources that don't end up being used, typo the pubmed id, or we fail to retrieve the source details via the API. Ideally, we could just delete these stub entries, but we'd want to make sure they were never used in a revision first. We should add the ability to either delete or deprecate sources to prevent them from showing up in browse tables, search results, and form autocomplete.

(Thinking about it a little more, deletion would be the ideal, but we'd probably still need to support deprecation for cases where the source had been used. It doesn't really make sense to build both capabilities, so deprecation is likely the way to go.)

[susannasiebert]

A couple of places where Sources are used that we shouldn't forget to check before deprecating:

• Features
• Molecular Profiles
• Variant Groups
• Source Suggestion
• Related Sources once Added the ability to add related sources #1219 goes live

[susannasiebert]

We should discuss whether this should be a user-facing feature like variant deprecation or an admin-only feature like disease or variant deprecation.

This might also be a good time to add the ability to edit sources (at least ASH and ASCO) to the admin console since those APIs have been locked down and these sources are not having their fields filled in right now. Making these sources editable in the admin console would at least give us a workaround to keep using these source types.