InCallUI: Enable Speaker on Proximity (3/3)

PS2: Recommendation From Peter Gregus
	on fetching proximity values
PS3: Ensure listener is destroyed
	&& attempt to fix issues with
	headsets still allowing the
	setting to activate...
===
restoring abandoned commit from:
https://gerrit.slimroms.net/#/c/15839/
PS: Fix logic

Change-Id: I2f0aab1dc66ed8297249e0858207ddaf63ef0d35

Conflicts:
	src/com/android/incallui/ProximitySensor.java
InCallUI: Speaker proximity only while in call (3/3)

Gives the option to only enable the speaker proximity
        feature during incall (speaker won't turn on
        while the phone is ringing, but will turn on
        after you remove the phone from your face, only
        after the receiving party has answered the call).

Change-Id: Ie1603f20ca306f0b08cf3f78b8593ac840a61179