Tres Gique: tag transition

[mdlbear]

From now on, I'll be using the short tag tg on posts that refer to Tres Gique in its current configuration (Tres Gique 2.0). I'll leave the older tag, tres-gique, to refer to the old version of the group. (Added: I may also use the long tag for things like gig and album announcements.)

One reason for doing this is to make it clearer when I use "tg-" as a prefix on subtopic tags, like tg-weekend.