Debugger: Also display dynamic QObject properties

Also, don't pre-compute the property count for performance
reasons. This leaves us with not too much information before
actually expanding the note, but better than waiting a
minute before seeing anything from a qwidget or such.

Change-Id: Ia39a01ec053ca821bb6cc76f09b3e836fa0d1b03
Reviewed-by: Christian Stenger <christian.stenger@digia.com>