mandatory/optional cannot be used as property names

[e-grigorov]

Recently, we switched to M4 build and got some new fails in our TCs. The problematic scenario is a property with a name: "mandatory" or "optional" i.e.

functionblock Testable {
	status {
		mandatory optional as boolean with {
			eventable : true
		} <NULLABLE false>
	}
}

or

functionblock Testable {
	status {
		mandatory mandatory as boolean with {
			eventable : true
		} <NULLABLE false>
	}
}

org.eclipse.vorto.core.api.model.datatype.Property.getName() returns null but should return "optional" or "mandatory" as a name.