Base: On-The-Go: Allow to toggle between front and back camera

Video Preview:
https://www.youtube.com/watch?v=MnPGn0zwpEw

In case you want to pick that feature, feel free to edit the
commit message to get rid of that ugly video ;)

Change-Id: Ia6422bf5bbd531240e62ee57de316a8e6f94546c
Conflicts:

	packages/SystemUI/res/values/custom_strings.xml
	packages/SystemUI/src/com/android/systemui/nameless/onthego/OnTheGoDialog.java