Improved functionality of sysML Parametric diagram (#293)

There is no way of displaying a constraint within the constraint property element, but perhaps only the comment notation complies with the standard.

Constraint property parameters, the text should be outside the symbol so that they look like ports (squared) but shown inside the border of the constraint property. Now the text makes the symbol grow and it looks no good. I have looked in the sysML 1.3 standard and at least I can find some examples of these diagrams that looks like this.