Pierce mullets can no longer have a different colour piecing

I think that this was broken when support for multiple colours was added. Need to correctly handle:

two mullets gules pierced or

For now this is being parsed as a modifier and a list of two colours. (although there is then an issue what it we really did want two pierced mullets, one of which is gules, the other or, that would have to be written as - "two mullets pierced gules and or"...? so the ordering is important here)