Settings: Security: implement a pin keypad shuffler [2/2]

this is to further prevent people using the tablet guessing your pin based on fingerprints left on the screen
example of the expected outcome - https://www.dropbox.com/sh/r3xb2q53ksaqni9/Oz1Eu8Dm7O

PatchSet:
- fix checkbox was wrong assigned
- enable only for PIN Password lock
- small cleanup of old code

PatchSet:
- cleanup

PatchSet:
- add modes.....disabled/always/on request

Change-Id: I225af5654c440aa16964df3257130febec6ef275
Settings: MediaScanner behavior on boot (3/3)

credits to corcoran, Slimroms

Change-Id: Ie380c12eace6bc743bebb3058d5248f06521a485