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

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

Change-Id: I9a3b4ff743bde05264d06042313da5f55f5ef765