SysUI : Fix opacity of LastApp Icon

Thanks to Nitroz for making alpha corrected versions of the
last app icon.

Change-Id: I2e8a9ae36e32f03aa36d3218c74d76b88123e64e
Signed-off-by: Zaphod <mwilson@acesappraisal.com>
SysUI:  Prevent Kill-Task from killing SystemUI.

If recents screen was active when Kill-Task button pressed, SysUI
was getting killed (causing wallpaper reset).  This
prevents SystemUI from being killed.

Change-Id: I3b669b29e5c244246ac02ad1ce6b4e39f7270aaa
Signed-off-by: Zaphod <mwilson@acesappraisal.com>