Basic Google Music Support

* Support for following operations: login, getting all tracks, getting url from track ID
* Settings page
* SQlite backend with search & global search support
Remove some duplicates in code, minor fixes
Fix Load all tracks method
All API Stuff moved to one class, some code refactoring
Playlist create, rename and delete features
Now you can drop your songs directly into playlist
Delete song from playlist feature added

(don't work, furtherinvestigation is required)
Fixed song deletion from playlist
Something something something dark side
Merge branch 'googlemusic' of github.com:blackjack/clementine into googlemusic