Fix bug in parsing EXIF data that's 'SRATIONAL'. (Including Exif:Brightness)
Add more EXIF fields we didn't support before. Also some minor reformatting.
Overhaul XMP parsing. Refactor to use PugiXML for more robust XML parsing.
It was very broken before.  Also add a bunch of new fields from the 2010
spec, I'd been working from the 2008 before.
Handle repeating IPTC tags generally, no more special case for keywords.
WIP fixing IPTC/XMP.
At this point, we aren't outputting all teh IPTC fields (still working on it),
but what we do output *is* read by Preview.App.
WIP IPTC
WIP IPTC - keywords working
WIP: IPTC