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 :)
There is a tiny optimization here by collecting the rules into a visible & hidden bucket, then inserting multiple identifiers for each rule type.

E.g.,
``
frameClasses.forEach(function(frameClass) {
   ...   
   if (displayValue === 'true') {
       visibleframeClasses.push(frameClass);
   } else if (displayValue === 'false' ) {
   ...
   }
});

function toCssSelector(frameClass) {
    return "draw|page[......] draw|frame[presentation|class=.....";
}
rule = visibleframeClasses.map(toCssSelector).join(", ") + "{ visibility: visible; }";
sheet.insertRule(rule, ...);
``

Consider this a thought exercise though... I do not forsee this block ever being particularly slow :-)