Adding font groups to font chooser

[Craig Drummond]

> I'd like to see overlapping groupings, with different types of
> categorisation such as monspaced, serif/sans serif in addition to things
> like handwritten, symbols, etc. A tree structure would allow easy handling
> of subcategorisation

The problem is that I'm not sure how to tell if a font is serif/sans - I don't 
think either Qt or fontconfig provide a mechanism for this. So the only 
usable sub-category would be monospaced/proportional  - and I'm not 100% 
convinced of the usefullness of this.

Craig.