Add a rendered and content rectangle properties to VideoOutput QML.

So you can align controls with an edge of the rendered area.  There's
also some convenience functions for mapping source to and from
destination coordinates. Also tweaked the updateGeometry function to
bail out if no input parameters have changed, rather than doing some
more boring maths.

Added a unit test for a lot of the class, too.

Change-Id: I943bb45e4e56356247d5d6deb5d446222edcb7ca
Reviewed-by: Dmytro Poplavskiy <dmytro.poplavskiy@nokia.com>

tests/auto/integration/multimedia.pro

@@ -4,6 +4,7 @@ SUBDIRS += \
     qaudiodeviceinfo \
     qaudioinput \
     qaudiooutput \
+    qdeclarativevideooutput \
     qmediaplayerbackend \
     qcamerabackend \
     qsoundeffect \