Added antibanish mechanics: as like other "diseases" that can be treated
with some useable items, banish will be able to be recovered as well.
Fixed some SQL issues introduced on the last commit, as well as
lingering inexistent ids on drop data. Fixed some concurrency issues
with MapleMapFactory. Set a ceiling for simultaneous items available per
map, where old ones are promptly discarded. Patched MWLB attack block
for higher level GMs.
As reported by J0k3r613, patched guild system not recognizing properly
the guild leader just after creation. Patched many more issues related
to guilds and alliances.
Fixed a bug on guild creation process where the leadership would not be
assigned instantly to the guild leader (would need to change channels or
reconnect to take effect).
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).
