Fix two annoying appbar issues:
- Appbar will collapse if the navigation sequence is too fast
- Tab ripple would paint over the indicator unless the ripple was unbounded [???]
Merge LibraryFragment, SongsFragment, and others into a new fragment
called HomeFragment. This is the beginning of the Auxio UI overhaul.
This has caused some regressions here and there, but these will be
rectified over time.
