* Added Track class.
* Query class uses and exposes Track objects.
* Result uses a Track object internally.
* Only log dtors in verbose mode.
* Make use of new Track class / api.
* Register Track class.
* Style fixes.
* These DBCmds don't need or want to use queries.
* Now-Playing signals can use tracks instead.
* Use new DbCmd interfaces.
* Allow to set PlaybackLogs when inserting items to PlayableModel.
* Updated Inbox to use new API.
* Don't double-check playback-logs for remotes.
* Don't be too verbose.