Move create folder and sort to overflow menu, cleanup back behavior.

Improved drawer management in reponse to back button presses:
- if drawer is open (and we didn't just open it), close it.
- if at top of root (and we didn't close root) open it.
- there's a timeout on this behavior such that pressing back
  a second time within a 1.5 second perior will NOT initiate
  the behaviors described above.

Change-Id: I5990848cd3047d9dc985ec10e57ab3a0f99ce79c