base: Add a key combo to start/stop video recording

Squashed commit
Screenrecord: Create the Screenshots directory if it doesn't exist
https://github.com/omnirom/android_frameworks_base/commit/d82898c6834b99fd3b400346bbbc4597d094814d

Press volume up and power to start recording a video of your screen.
Press this key combo again to stop it.

Change-Id: Id0b13ba1092a1d6e0bf7bff5f14d89764cdf370c

Conflicts:
	packages/SystemUI/res/values/custom_strings.xml
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java