docs: Android 4.3 Platform Release Notes

In addition to platform notes, modified the SDK Manager update
warning to advise downloading of SDK Tools 22 or higher. This
dependency is based on the updating of the SDK repository
schema. The last update was repository-8 with the SDK 22.0.0
release, according to raphael@.

Change-Id: Icaaf39a6d49eccdc926aa4c4249db8a0b1d095a7