screenshot: quick delete action

Add option to delete screenshot from notification

Change-Id: I0f153bc3c72b902163b4ae75e220ddb09e3fcb11

Conflicts:
	packages/SystemUI/res/drawable-hdpi/ic_menu_delete.png
	packages/SystemUI/res/drawable-xhdpi/ic_menu_delete.png
	packages/SystemUI/res/values/screwd_strings.xml
	packages/SystemUI/src/com/android/systemui/screenshot/DeleteScreenshot.java
	packages/SystemUI/src/com/android/systemui/screenshot/GlobalScreenshot.java