Implement ChooserTargetService querying for ChooserActivity

First cut at querying services provided by apps that offer
ChooserTargetServices. This first implementation provides no ranking.

Bind to a limit of 5 ChooserTargetServices and offer the
ChooserTargets they provide as options in the system
ChooserActivity. The chooser now presents targets as a grid and
displays the activity icon from the referrer activity.

Change-Id: I45db829f184fc78d4f18d42b2a60b25bc301eba8