Added get-headers.sh and hags script for managing android headers and package versioning.

Signed-off-by: Tom Swindell <t.swindell@rubyx.co.uk>
Updated hags to go back to "master" branch when finished.

Signed-off-by: Tom Swindell <t.swindell@rubyx.co.uk>
Merge branch 'master' into libhybris-aosp-android-4.2.1_r1.2-master