SystemUI: Use EdgeGesture service to trigger Pie

EdgeGesture service triggers Pie when detecting gestures on
the WHOLE edge, not just the center.

Patch Set 2: Better trigger values

Change-Id: Id7d9d7f6f5a37ca3696cdddf0da78c88c067970e

Conflicts:
	packages/SystemUI/res/values/config.xml
SystemUI: Position Pie at gesture's triggered position

As the EdgeGesture service is triggered at the whole screen
edge, place Pie at the gesture's triggered position, instead
of always positioning it at the center of the edge.

This might be controversial and a matter of taste, but in
particular on tablets it's sometimes hard to hit the exact
center of the edge and therefore gestures often fail. Could
also imagine enabling this feature on tablets only. Needs
some discussion...

Change-Id: Ife28ac434667148583b34bcccd11262c111b5a67
PhoneWindowManager: add ability to use EdgeGestureService for system gestures.

Update: Default to enabled

Change-Id: Id4e2c0d82f771cd1c20e9196fb6db347494cca69

Conflicts:
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java