Keyguard: remove duplicated code

Patchset 2: fixed whitespace error
Patchset 3: a few more tiny changes
Patchset 4: some code moving, removing an unnecessary member
Patchset 5: make toggleSilentMode() a bit easier to read
Patchset 6: revert most of the cleanup
Patchset 7: fix syntax error
Patchset 8: fixes pointed out by Danny Baumann

Change-Id: I4e5f8c92b223c1260891472dbf807d5ff53e5721
Notification sound-to-vibration conversion toggle

Allows to change the new feature of AOSP 4.2, where all notification are
changed to vibrations on vibrate mode. Instead, allow the old behaviour
to silence sound notifications and to only play vibrations if desired.

Alle credits go to romanbb from AOKP, I just ported it.
Original AOKP-Commit:
https://github.com/AOKP/frameworks_base/commit/c1b2bb9b5d0c33e790973841bb2acaa5ea5d51fe

Change-Id: Id27dd2975d3383f6d7395a0ee995d7832e87ca66