Avoids one extra uneeded renegotiation if the elements are already
configured to their final property values when the caps event
goes through.
Also avoids hitting bug https://bugzilla.gnome.org/show_bug.cgi?id=748344
It contains videocrop ! videoscale ! capsfilter and implements digital
zooming.
At this moment, it is a private element of the camerabin plugin.
This will remove some code used in wrappercamerabinsrc to make
code clearer and digitalzoom can potentially be used by other
applications in the future, it has nothing camerabin specific.
