Revert "add configurable headset hook to buttons"

Toggling whether the headset button works or not is like
    "toggling whether or not the volume buttons do anything"...
    especially with the default being to do nothing with it pressed.

find me a user that is bothered by their headset button doing what they expect
     when they press it, and I'll consider revisiting this.

This reverts commit d02ca4d595783fdbd1db397cd148b0fc5b79b186.

Conflicts:
	res/values/vanir_strings.xml
	res/xml/button_settings.xml
	src/com/android/settings/cyanogenmod/ButtonSettings.java

Change-Id: Iba2462130e8f7ed0d4821507d35c2e59d322240f