...tap tap, is this thing on?

Introducing themes!
* changes alignment and background drawing in the QGV to allow themes with bg color other than white.
* clean up ugly code in Scene (width()/width() is rather silly)
* Finally, only use one QSvgRenderer!
* change theme file format to only use one svg
* centralizes theme handling code to One Single Spot(tm) in the ctor of Scene
* introduce new theme "spacy"
default theme is the old "scribble", to change run "bovo -theme spacy"