SystemUI: Add double tap to sleep gesture

Change-Id: I4c54718e8ec8774677d13917b3a7ffa3b4b18cb5
screenshot: quick delete action

Add option to delete screenshot from notification

Change-Id: I0f153bc3c72b902163b4ae75e220ddb09e3fcb11
Show confirmation for deleted screenshot.

Change-Id: I4a36cf06bf252e5e15fe08fbd054dc64a0a507ae
Runtime toggle of navbar

This adds the framework support for enabling the Navigation bar
on devices with hardware keys. It is toggled from Settings, and
depends on device-specific support for the KeyDisabler hardware
control

Change-Id: I88fecb2ca1e8613591c327a93f53909b00239cd8

wm: Nullify hardkey function assignments if enabling the navbar

This caused erroneous (and sometimes duplicate) events being generated
due to the regular key function assignments. The navbar does its
own action management, so don't try to derive from the actions
usually present in hard keys.

Change-Id: I82866e24547f8145cac4f07820ae90aacce09281