Repairs: gear comes before the group

Characters now watch their gear's wear: in the red, they visit the repairer before following their group, the leader takes the whole showcase group there, and repairs are done item by item when gold is short.

Fixes

Gear in the red (average under 40%, main weapon or three items broken): visiting the repairer comes before following the group. If a showcase group member needs it, the leader takes everyone there.
Not enough gold: worthless items are sold first, then repairs are done item by item, from the weapon down to accessories.
After a death with broken weapons: the character runs back to its corpse instead of using the graveyard spirit healer, unless the spot is dangerous.
Unusable vendors: a vendor that is transformed, dead or hostile (Pyrewood villagers turn into worgen at night) is ignored, for every service.
Monitoring: each character's gear wear is published continuously and a detector reports any gear below 20% for more than 15 minutes.

Verification

On the test server, two showcase members cloned with broken gear went to repair on their own right after logging in, then rejoined their group. Paired validation on 20 clones: experience, quests, gold and deaths stable, no crash.