Improve BUML Validation for “Invalid multiplicity values” issue

[AtefehNirumandJazi]

When importing BUML model with the “Invalid multiplicity values” issue, error is not displayed in the graphical environment. For example:

I considered this incorrect part in my model:
taught_by: Property = Property(name="taughtBy", type=professor, multiplicity=Multiplicity(0, 0)) # ERROR: Invalid multiplicity

[ivan-alfonso]

We need to validate and generate an exception when the max value is less or equal to 0

[jcabot]

Added the max multiplicity check