Trade Logic: Missed a type ctor

Trade Logic: Missed a type constructor

I forgot one type constructor before, the one to construct the type of predicates. It was covered by "One of the exposed primitive types", but inadequately. It needs to can express a predicate's type parameters.

Rather than mixing applications and literal lists, or requiring list at the beginning of each list, I will use low-quote and write:

,(pred . Args)

where pred is the symbol pred and Args is a type (named or literal) augmented by mode annotations. This type accepts any predicate whose inputs are all equally or less strict than the respective parts of Args and whose outputs are all equally or more strict than the respective parts of Args. It would also reject predicates that had no equivalent mode.

For example, the type , (pred type +type) would accept/reject various predicates:

Arg1 type	Arg2 type	Disposition
type in	type out	Accept
thing in	type out	Accept
thing in	thing out	Reject
thing in	type out	Accept
thing in	type in	Reject
type out	type out	Reject

I may need to do more for the interaction of the mode system and the type system here.