Allow system apps to add to settings dashboard

Allow system apps to add a tile to the top level of settings that
links to an activity through adding a filter for a specific action.
Determine the info for the tile based off manifest info for the
activity. Also allow the same for managed profiles, but show a dialog
in between to select which profile.

The category in which the item is to be placed must be in meta-data.
The icon and title can be specified through meta-data as well or
if unspecified the activity's label and icon will be used.

Also added an optional <external-tiles> tag to the dashboard
category xml, this allows Settings to put external tiles
in the middle of some categories (Personal does this).

Bug: 19443117
Change-Id: Idc9938d1549d181103a3030a8784b527215a8399