Create CSS rules for the attributes presentation:display-*

Improves the display of many of my test ODP slides :)

Also achieves pretty similar results in LO and the viewer for
https://wiki.gnome.org/GUADEC/2014/LightningTalks/SlideDesign?action=AttachFile&do=view&target=lightning_talks.odp

Once this is in and 0.5.2 out, they will have no excuse not to use ViewerJS for their webpages and even presentations :)
This should have a more specific name such as ``insertCSSNamespace``