Add qUUID docs

[jonbarrow]

Adds docs for the qUUID type. So far this has only been seen in WATCH_DOGS on the Wii U, but since Ubisoft uses it for their Uplay profile IDs in that game it's likely that this exist in at least other Ubisoft games

This doesn't document the red-black tree usage also seen in WATCH_DOGS when using qUUID types, as I have no idea what that's all about. It seems like WATCH_DOGS creates a red-black tree for each qUUID, but it's not clear what purpose this has. The game only seems to do this when extracting the qUUID from an RMC message, as it does not do this when creating a qUUID from a string for example. It also seems to not do anything with the tree when encoding the type?