Rename the Rectangle element's border.aligned property to
border.pixelAligned to be consistent with the Flickable element's
pixelAligned property.

Change-Id: I916a47416c558f9a96f7b966c344525db984a85f
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>