Add autoplay_app domain

Initial check in of empty autoplay_app.te policy file.

Create isAutoPlayApp input selector. Give this selector high precedence -
only below isSystemServer.

Add neverallow rule disallowing an app context with isAutoPlayApp=true from
running in a domain other than autoplay_app.

Change-Id: I1d06669d2f1acf953e50867dfa2b264ccaee29a4