Advertise MPD with Avahi

A rudimentary implementation to resolve #39, ignoring dbus errors (just restart), name collisions (choose a fresh name), etc.
Add genre, composer, and performer tags and use them
Merge remote-tracking branch 'upstream/develop' into feature/extra_tags
Date is not mandatory AFAICT
Split artist and albumartist dependency, update tests based on this
Fix flake8 issues
local: Remove debug logging in tests
local: Formatting
Merge branch 'split_albumartist_artist' into develop
docs: Update changelog
Rename track in MPD to track_name to avoid confusion
Update filter name to match track_name change
Merge branch 'rename_track' into develop
docs: Update changelog
Merge branch 'develop' of https://github.com/mopidy/mopidy into feature/extra_tags
Fix testcases after merging mopidy/develop
Merge branch 'master' into develop

Conflicts:
	docs/changelog.rst
Added a ton of extra tests and expanded a few to include new tags
Add missing regexp
Add frontend MPD tests for 'search comment "foo"'