Add missing files to branch

Test for model with Error RingSelfInt. Gets Vertices and BoundingBox

extending visitor and add abstract visitor

Update file TestExample

Extend file by InnerRing

Cleanup Visitor implementation

See merge request !33

Transfer the basic cpp code skeleton

Use as guideline for code conversion

Resolve "Update Dependencies"

See merge request !31

Visitor rework

See merge request !30

CopyHandler and the Copyable-Interface are obsolete due to Copy.copy
offering the object-copying functionality with serialization.