frameworks/base: Update quick launch shortcut icons/resources

Update the existing icons and add "xxhdpi" versions created
from a vector template. This commit cleans also the resource
files a bit up.

Screenshot: http://goo.gl/6CrMYr

Change-Id: I45abee5cf13cd239eb5b4402019afac28d6d5952
Allow subclasses to override bindPreferences().

Allows them to modify adapter behaviour.

Change-Id: I6767e3988740b674fbdf40a903cd2ef3949ca7db