Minor clean-up of worker update logic

Improves messages and adds an additional trim() check.
Adjust update formats

Enables more fine-grained update resolution in the future if needed.
Update documentation links

These now include the new website (and the Anki add-on forum, too).
Fix documentation error

There are no longer any 400 errors in the unresolved module.
Add AGPL license boilerplate to web subproject

Inserts the boilerplate to all files in the web subproject that support
comments of some sort.