cmsdk: Add CMAudioManager

 * This is a rework of the session callback API which previously
   lived in the framework due to JNI usage. This has been split out
   and cleaned up for CMSDK.
 * The JNI library lives on the server side, and the app-level
   callback has been changed to a protected broadcast. This allows
   us to wake up registered services when these events occur.
 * Additionally, we support listing all active audio sessions.
 * Also brings some JNI love/hate over to CMSDK.

BACON-369
OPO-644
Change-Id: I31c293943474419e3db088bb7ffab75f7440ac0f