Factory refinement types

[jonhue]

Allow refinement types to act as factory and be instantiated in different circumstances with varying parameters.

# define as
type GreaterThan<a>(x :: a) := [y ~ a | y > x]

# use as
GreaterThan<Number>(5)

Can only be instantiated with literals.

Also allow instantiated parametric types on the right hand side.

[jonhue]

depends on #16