Move to "G+-style" selection.

To select an item, click the checkmark that overlays on rollover.
To navigate, just click anywhere else on the item.

Also move selection from additive by default rather than exclusive.

Change-Id: I47e6ca1942fe1fdaaf615f6ab0e0a547f1a51735
Add diskPack as a high level local storage destination, and storage-filesystem based sync queue

Change-Id: I9ec0583b160f89952cdad851e66c7fabf22b7bb4