Start adding predicates for optional types (not complete yet)
Start adding predicates for optional types (not complete yet)

jjdekker/libminizinc,jjdekker/libminizinc,jjdekker/libminizinc,nathanielbaxter/libminizinc,nathanielbaxter/libminizinc,nathanielbaxter/libminizinc,nathanielbaxter/libminizinc,tias/libminizinc,jjdekker/libminizinc,tias/libminizinc