OpenStore

// Open oStore for oPC.
// - nBonusMarkUp is added to the stores default mark up percentage on items sold (-100 to 100)
// - nBonusMarkDown is added to the stores default mark down percentage on items bought (-100 to 100)
void OpenStore(object oStore, object oPC, int nBonusMarkUp=0, int nBonusMarkDown=0);