Added cycleName attribute to set.

Adding the attribute should have no impact on OCTGN, but allows to know which cycle the set is a part of.
OCTGN data files are used as source material by other softwares (such as the deckbuilder I maintain), and this would be a welcomed addition that could also be used by OCTGN.

--- As a side node, I tried to use GitHub for Windows to create a branch but I apparently don't have the rights to do so. I can through the website but I'm limited to 1 file per patch-X branch (unless there's something I've done wrong).
Anyway, if this commit is validated, I'll update the other sets as well (or we can discuss a better place to put the cycle name).