updates and how to build a single apk

Change-Id: Ibd2b332fdd70fcad935124fd24deba6d002b874d
new build apk script

Change-Id: I1284503c80c24b71bb6be743413a42357d581865
improved message

Change-Id: I65c9a10f76bb485a892164be1a182e0684bef356