Moved data functionality to AppPermissionViewModel

Moved data generation and processing from AppPermissionFragment to
AppPermissionViewModel. Also expanded equals method for
AppPermissionGroup and Permission, and changed how AppOpLiveData gets
its UID. Finally, changed AppPermissionGroupLiveData to initialize its
AppOpLiveData only after it has verified the Package and Permission
Group are valid.

Test: manually open App Permission Screen
Change-Id: I40ed876d7c6c7ec6cb7a06f804e27f9fe23c211b