[nemo-qtmultimedia-plugins] Ensure new nodes have valid geometry.

Set the geometryChanged flag after creating a new node otherwise its
geometry won't be initialized unless something else coincidentally set
the flag.
Merge pull request #5 from adenexter/master

[nemo-qtmultimedia-plugins] Ensure new nodes have valid geometry.
[nemo-qtmultimedia-plugins] Port to GStreamer 1.0