Support importing Universal VTT (UVTT) files

[esemwy]

Apologies if this is already supported and my search-fu is at fault. It would be awesome to support the type of UVTT files provided by Dungeondraft and Arkenforge. I run online campaigns as well, and I’d rather not setup my walls and such twice.

[luiscastilho]

Nice! I didn't even know such a format existed. I will check it out and see if I can add support to it.