* fix crash because of incomplete inheritance of BlendPoint and BlendCurve -> do not inherit from BaseClass
as consequebce make destructor non-virtual and remove getPyObject
* pass std::vector by const reference
* remove unneeded includes
* use more suitable Python exception types
* when returning with null from Python handler then set an exception
* harmonize file guards
* several optimizations or simplifications
* use modern C++
* harmonize command name
* fix copyright note
