InCallUI: Add "Answer Via Speakerphone" Glowpad Target

Change-Id: If8bdb14f1df386272c9b16816175322ecda2fa90

Conflicts:
	res/values/dimens.xml
InCallUI: enable navbar while call is incoming

since we have back-button support to send incoming calls to
the statusbar, we need to make sure the navbar is actually enabled
while a call is incoming, otherwise that feature is totally unavailable
on devices that do not have hardware back button

Change-Id: Ibe58efadb06232baabca211078e14ba45360c298