android/README: Update documentation with AOSP 4.4
android/README: Update documentation with AOSP 4.4

This includes:
 - sample repository to AOSP 4.4 based repository with support for
   Nexus 4 and Nexus 7 2013 devices.
 - adds info about snoop service
 - other random additions

ComputeCycles/bluez,mapfau/bluez,silent-snowman/bluez,pkarasev3/bluez,pkarasev3/bluez,mapfau/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,silent-snowman/bluez,ComputeCycles/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,silent-snowman/bluez