Settings: fix typos in strings

Change-Id: I556f29f7c58b431998bad9866a4e4d092a50ab63
Settings: fix media scan on boot behaviour

The settings reorganization patch forgot to move the actual java
code for this preference to the Memory class.

Add respective code and clean up old unused code.

Change-Id: Ic1b8251e45990514bb51a2ff07f5c9a12fae32bf
Merge "Settings: fix media scan on boot behaviour" into kk4.4-caf
Launch SuperSU from Settings