Settings : Add hooks for device specific features

Add support for :

Devices with bluetooth input peripherals
Devices with screen gesture support
Devices with a back touchpad

Conflicts:
	res/xml/language_settings.xml
	src/com/android/settings/cyanogenmod/ButtonSettings.java
	src/com/android/settings/cyanogenmod/SystemUiSettings.java
	src/com/android/settings/inputmethod/InputMethodAndLanguageSettings.java

Change-Id: Ia4835c69a8ba8fb76597e0ab0540f8ef1ed6e322

Conflicts:

	res/xml/system_ui_settings.xml
	src/com/android/settings/inputmethod/InputMethodAndLanguageSettings.java
Add option for switching between UMS and MTP/PTP mode. (2/2)

This adds support for switching between UMS and MTP/PTP.
Settings part (this part) adds option in USB settings (statusbar/notification drawer) for enabling UMS,
and adds setting in Storage menu to enable / disable UMS, this since the USB settings page disappears when enabling UMS.

Forward port from cm-10.2, adjusted for 4.4

Change-Id: I6cf50a41a9a82e40e702f5231ce663636c149613

Conflicts:

	res/values/cm_strings.xml