android.permission.ACCESS_SUPERUSER and /data/local/userinit.d

Added usage of superuser permission.
For usage with bundled superuser app in CM-10.1

Added creation of script in /data/local/userinit.d/.
Enable of mulitple users will survive reboot/reflash of ROM.

Tested on Motorola Xoom 3G(MZ601) running CM-10.1 nightly.

Best Regards
/Erik