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Pre-existing c++ escape sequences in the XML files have been replaced by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.
add convenience method getAllDerived()
support TypePy asrgument in getAllDerivedFrom() and isDerivedFrom()
return TypePy instead of str in getAllDerivedFrom()
