Fixed some oddities with other player clients when dealing with summons
(spawning, taking damage or attacking). Fixed damage dealt to player not
apearing if the player is a GM on hiding and other players in the area
are GMs as well.
Fixed performance drop on the server when trying to level up equipments
which has high stats points. Added a flag enabling massive damages with
Three Snails skill.
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).
