Make it possible to hangup and dialback from IncallScreen

Add slider action in the InCallTouchUi to hangup on the person calling
and immediatly call him/her back.
Add preference to enable and disable this feature

Change-Id: I6db830fc2b063caace6631945a4442e8d87664e0

Conflicts:
	res/layout/incall_touch_ui.xml
	res/values/cm_arrays.xml
	res/values/cm_strings.xml
	src/com/android/phone/PhoneUtils.java