ConstraintType::checkArgTypes() allows a constraint type to perform type checking on the arguments that are passed to a constraint. This is used by the parser at compile time to perform type checking.

currently only the AbsoluteValue and AddEqual constraint take advantage of this, we need to implement it for all subclasses of Constraint that are exposed to the user.

See ModuleConstraintLibrary::initialize for registration and Constraints.hh/.cc for definition.