README: add manta
Updated to android-4.2.1_r1.2

Manifest for android-4.2.1_r1.2

Change-Id: I692f106ca245e411e452d39104af4d0b71ef0fd8
Merge branches 'sj4.2.1' and 'sj4.2.1-staging' into sj4.2.1-staging