nocashshop mapflag

As requested by the community in http://hercules.ws/board/topic/1477-mapflag-for-cash-shop/ and http://hercules.ws/board/topic/1476-disable-cashshop-in-pvp-woe/
'nocashshop' mapflag disables the usage of the cashshop button as well as any attempts to purchase (in case the flag is turned on after someone gets the shop open).

Signed-off-by: shennetsind <ind@henn.et>