Now all escaping required for the C++ code generation is done when the
.cpp/.h files are generated. Previously, only newlines were escaped
automatically. This was a) inconsistent and b) leaked c++ details into
the xml data.
In addition, the escaping is now done in one central place, harmonizing
the three previous implementations.
Pre-existing c++ escape sequences in the XML files have been replaced by
their literal equivalent so that the resulting python doc sting remains
unchanged.
fix inheritance of MeshFeaturePy
fix inheritance of PartFeaturePy
remove useless test() method
implement getPyObject in GeoFeature in case a sub-class doesn't implement it
