Use accurate county names for Wales

I'm assuming that whoever first added the Welsh counties doesn't live in Wales... :)

The previous "Preserved counties of Wales" referenced and used don't have anything to do with today's postal addresses and are not used in daily life. According to the wikipedia article (where they were presumably taken from) they are "for the ceremonial purposes of lieutenancy and shrievalty."

I've updated them here, and added Welsh translations for them.

P.S. I previously created a pull at django/django-localflavor-gb#5 but I guess I didn't read the warning clearly enough. It should be higher up on the list or not indexable by Google. A stupid waste of time :(