Added the PIN feature. Fixed ranking now calculating ranks now
world-based instead of overall. Rebalanced equip exp gain and made
cosmetic equipments no more leveling up (cosmetics leveling up are
useless).
Added true protection against race conditions on player trades and fixed
some situational issues. Character's quest status table also received
concurrency treatment. Quests with time limit now expires properly.
Increased subtly the performance on the server start-up.
