Add navigiation to LibraryFragment. This navigation is nested so that one can still move through the ViewPager, which will certainly have no problems later on. /s
Remove MusicRepository/All Library models and replace it with a single shared ViewModel, Move MainFragment into MainActivity, and remove the LoadingFragment -> MainFragment navigation path.
Turns out a dedicated Now Playing screen wont look that good, so refactor that into the Library screen. Also replace the ActionBar with a Toolbar and update the theming a bit.
