Added optional parameter 'flag' for shop NPC (bitmask):
-- 1 = Disable Discount
-- 2 = Disable Overcharge
-- By default (if flag is undefined), the value always be 0.

Sample usage:
prontera,147,167,6	shop	Shop 1	872,2102:-1,2104:-1,501:-1,3
prontera,147,164,6	shop	Shop 2	872,2102:-1,2104:-1,501:-1,2
prontera,147,161,6	shop	Shop 3	872,2102:-1,2104:-1,501:-1,1

Signed-off-by: Cydh Ramdh <house.bad@gmail.com>