Update DirectoryFragment to use RecyclerView.

Add MultiSelectMaanger class to manager selection on a RecyclerView instance.
There are several outstanding issues that still need to be addressed
surrounding Grid mode as the GridLayout manager doesn't support
automatic column count calculation.
Also, we're missing the puddle effect on touch...
And probably other stuff. But it all *mostly* works.
Oh, also. Footers are currently commented out.
Add traditional unit tests for MultiSelectManager.

BUG: 22225617
Change-Id: I3cd26a10683f42053556d463a5d2f0d2a0bbde84