Suggestion: add the "Concepts" wiki page to the official documentation

I really think the content of https://github.com/beetbox/beets/wiki/Concepts should be added to the official documentation, I wish I found it earlier! :)

These concepts can be quite non-obvious for the novice user, accustomed with the workflow of other music tagging tools (no separate database, edit/write metadata directly into the files, exit and let the user move those files around in the filesystem manually).

Possible locations?
* as a new initial chapter in the "Guides" section?
* at the beginning of the Guides -> Getting Started chapter?