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 mechanics for the EXP/DROP cash coupons (such as enabling
out-of-time active coupons via command and automatic update of active
ones over the designed interval). Created MapleCouponInstaller as means
to gather info about the coupon intervals and rates from the WZs (the
generated SQL table is already updated on the db_database.sql file).
