SpecializedItemTypes for currency containers

[Toirealach]

If GetItemLinkItemType() returns an ItemType of ITEMTYPE_CONTAINER_CURRENCY then
the SpecializedItemType which the function returns should tell us which currency
is in the container, e.g.:

SPECIALIZED_ITEMTYPE_CONTAINER_CURRENCY_MONEY
SPECIALIZED_ITEMTYPE_CONTAINER_CURRENCY_CHAOTIC_CREATIA
SPECIALIZED_ITEMTYPE_CONTAINER_CURRENCY_TELVAR_STONES

etc. for any all types of currency containers that exist in game.