Management actions, invalidate caches.

In manage mode, touching launches a VIEW intent for the file.  Also
adds actions for sharing and deleting.

Move roots and thumbnail caches into Application object, and flush
cache when thumbnail size changes.  Listen for package changes and
broadcasts that should invalidate our roots cache.

Pick default grid/list mode based on provider hint.

Bug: 10329983, 10330210, 10378834, 10330069
Change-Id: I75afb1c58ab71bb9d55852b1059da7257a376248