Define security labeling for isolated processes.

Used when an app service is declared with android:isolatedProcess="true".
Place such processes in a separate domain, and further isolate them
from each other via categories.

Change-Id: I1d64f8278f0619eedb448f9a741f1d2c31985325
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>