Add Quick Settings USB Tether tile (2 of 2)

Patch Set 8: Make tile dynamic

- Thanks to Björn Lundén for the drawables

Change-Id: I414848f6cb8a789d0b5edfcb79ab53cb85ebc20e

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/QuickSettingsController.java