Abdula is now the Skillbook announcer NPC. Fixed some inconguencies with
the isInJobTree function, now properly returning if a skill id does make
presence on a player's current job path or not.
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).
