Feature/beets interface

As stated a few weeks before in the chat, I worked on a interface between Ampache and beets.
New Catalogs:
Beets: This is the local one. Works if on the same machine. The web Server must have access to the Music on the file system and the beets Database.

Beetsremote: Uses the API from the web plugin from beets. Should work with remote machines also, but I couldn't test this. The Music will be streamed through ampache, the Listener may not have access on the beets Web Server.

Any comments and improvements are highly appreciated :-)