MediaProvider: MediaScanner behavior on boot (2/3)

Lets you enable/disable/ask (with a notification) media scanning on boot.
Can speed up boot and reduce initial boot lag from MediaScanner

- added xxhdpi icon
- no need for multiuser due that this should be a one time set
  general option set by the owner of the device

Change-Id: Iad0b72f8b653b3d567b27de3ccf5c6cfb07e40ed
MediaProvider: google please cleanup your translations....MediaProvider cleanup

it is really at the moment a nightmare to see compile errors when
getting 100000 of warnings. Whatever we removed already on some
packages the warnings....but still a lot are there

Change-Id: I8f25954c240300d74cf8acdd8f3e86b62c4928af

Patchset: 1
https://gerrit.omnirom.org/#/c/3706/