SYSML2 — View::viewpointSatisfactions should subset viewpointChecks and checkedConstraints

In the Views::View model as submitted, viewpointSatisfactions was accidentally declared as redefining viewpointChecks. This should be changed to subsetting, so that there can be (non-composite) viewpoint references within a view that subset viewpointChecks but not viewpointSatisfactions.

Further, because View is a kind of Part, viewpointSatisfactions also has an implied specialization of Item::checkedConstraints. It would be better if this was explicit, to make it clear that any declaration in a View subsetting viewpointSatisfactions automatically satisfies the requirement to subset checkedConstraints, so that this does not require an additional implied specialization.