Fixed issues with negative experience being distributed to characters
when killing a mob, rendering "Exp reset". Fixed chaos scroll behaving
oddly. Refactored debuff expirations to manage one list with registered
debuffs and expire times, thus lifting some load from the TimerManager.
Added concurrency protection on how World deals with parties. Thanks to
the DietStory dev team, fixed some issues with the MK maps.
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).
