Added basic model objects for tracks, tags
Allow many-many track/tag reln's; clean up helper
Added simple DAOs for tracks and tags

DAOs are untested. Models updated to work better with DAOs and expected
future changes
Added tests for TrackDAO
Clean up Track DAO and its tests
Tag implements a data source. Missed in last commit
Added full tests for TrackDAO

Merged in TagDAO; reimplemented Track and Tag: IDs are now fundamental
to them.
Track stores its tags as a multimap
Address pull request comments: minor changes
Merge pull request #3 from patrick-conley/259-implement-a-dao

259 implement a dao