Add cardinality constraints to ReContainers #15
Description
We should have arbitrary min and max values applicable for our lists - and a way to specify the necessary or not property for all singleton containers when we define them.
The available cardinalities should match those of EMF.
Write consistency checks for all of them, that also set the found errors on each model element. This way, they are later usable for graphical highlighting of model errors.
If possible, now also handle addition introduced errors so that models stay consistent. if you think that this is not a good approach, write a version that blocks instead if someone inteds to violate a constraint.
This way, we would have a "checked" version and an unchecked one. If this is also ahrdly possible, we will move the burden to the framework user - just like EMF does.
might be good to solve together with #14