cmsdk: Add CMParts API

 * Add a Preference subclass which queries CMParts and handles all
   the work needed to add a new part into Settings with a single
   line of XML.
 * The parts list lives in the CMParts app as res/xml/parts_catalog.xml
 * We also support receiving a broadcast to update the title/summary.

Change-Id: Iaceddc85272718ba93e4086cc2577c3b016419e2