It became necessary in order to have different types for Tracks vs Albums,
instead of just differentiating by isDirectory: Boolean.
Also:
* Fix Album display in SearchFragment.kt
* Use same ids in all lists
* There is one database for each Server
* Index items are saved with a "musicFolderId" prop, which makes it possible to filter the database by musicFolder without necessarily having to query the server for it.
* Databases for new Servers are created on the fly
* If the user removes a server, the respective database is deleted.
instead of reusing an old one. This lead to a crash.
Also make the AlbumList use the correct placeholder,
remove an unused resource file, and update the placeholder to look less clumsy.
* Splits former SelectAlbumFragment into separate fragments for Albums and general collections of tracks
* Renames and refactors SelectArtist view to extend the new Generic classes
* Adds error handling (Fixes#484)
* Adds EndlessScrolling capabilities to all Album Lists
* Uses RecyclerViews and LiveData for performance and in-memory caching
* Refreshes the UI to be aligned with the ArtistList UI
* Add a new GenericEntry to the domain data classes, and make other types extend it
tzugen