Add support to specify default values for function arguments

As the title states.

Before merging, we could think about if other methods should get default values as well. The current selection is the same as in VAMatlab.

scripts/templates/wrapper.py.j2

@@ -99,12 +99,12 @@ class VAInterface:
     {% for method in methods %}
     def {{ method.name }}(self,
     {% for arg in method.args %}
-        {{ arg.name}}: {{ arg.type }},
+        {{ arg.name}}: {{ arg.type }} {% if arg.default %} = {{ arg.default }}{% endif %},
     {% endfor %}
     {% if method.kwargs %}
         *,
     {% for kwarg in method.kwargs %}
-        {{ kwarg.name }}: {{ kwarg.type }},
+        {{ kwarg.name }}: {{ kwarg.type }} {% if kwarg.default %} = {{ kwarg.default }}{% endif %},
     {% endfor %}
     {% endif %}
     ){% if method.returns %} -> {{ method.returns }}{% endif %}: