Added in rudimentary category support for dotdesktop file emitting; ie: PXML's catego...

Added in rudimentary category support for dotdesktop file emitting; ie: PXML's category will pass through a new config file that attempts to map them to a freedesktop standard category
Also included some possibly sensible defaults for categories
Fixed a hard to spot parsing bug in pnd_tinyxml (& instead of |, bad dflem ;) so categories are pulled in correctly now
- really, we should fix up the pxml struct (and disco struct) to have trees instead of fixedcount fields
- really really, we should fix disco-t to be derived from pxml-t to avoid the duplication; when it was simpler I thought it was a good idea to separate disco and pxml structures, but they're too fat now :/