[1/2] base: Power Menu: Add Screenshot Option

Adding Screenshot menu and functionality to Power Menu

Change-Id: Ic09c2f4eb1a3d3de825de638fa43f4158736a320

Power Menu: Add Screenshot icons for xhdpi, hdpi, ldpi and mdpi

Change-Id: I58f39b14995ca2ea78ca9a1c92f86de3e32c7cb9

Using Settings.System instead of Settings.Global for settings constants

Change-Id: I96e24d063f139c01b15b0a639c87c10d0f690106

Corrected Code formatting Errors

Change-Id: I96e24d063f139c01b15b0a639c87c10d0f690106
Merge "[1/2] base: Power Menu: Add Screenshot Option" into android-4.4
merge changes from Omni 4.4 into local branch