Merge pull request #144 from mdlayher/master

Add ToString() for all models
- Added support for scanning album artists
- Added album artist api call
- Added beats per minute, lyrics, and comment fields to song objects
- Fixed artist and album names with varying extra whitespace were scanned as different items, now trimming all whitespace for artist, album artist, album, and song names
- Added total scan time to folder scanning metrics printed after scan completes
- Fixed various bugs in the new album artist implementation
- Cleaned up some ApiHandler code