Filter out constructors from abstract classes

[Matthias Schoettle]

Consider an abstract class with a constructor. And a concrete sub-class with a constructor.

When creating a new lifeline with a message, it is possible to choose the metaclass lifeline of the abstract class and select the constructor.

However, this should not be possible. See example model attached.

I.e., the constructors of abstract classes should be filtered out.

[Arthur Le Saint]

Resolve #428: Filtered out constructors from abstract classes

→ <<cset 0010fac3cb43>>