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, changed the
position in the menu and the label.

Original AOKP-Commit:
https://github.com/AOKP/packages_apps_Settings/commit/e92446576c2dfbe51089287c43c3f799b5cc0057

Patch set 1-6 : Initial commits
Patch set 7   : Better wording of the summary string
Patch set 8   : Lower case app

Change-Id: I267fc4b62ff045f305cf29c1b4f365e91f7cf1db