This adds several enhancements to ParaView's Python-based programmable
1. Python Algorithm (or `VTKPythonAlgorithmBase` subclasses) are now
supported. Users can develop algorithms in Python as Python classes.
2. Decorators can be used to decorate Python algorithm classes and their
methods to declare the proxy/property definitions needed to use such
Python algorithms in ParaView as sources, readers, writers, filters.
3. Python modules can be loaded directly as plugins. If the module
has any Python algorithms that are appropriately decorated to be
exposed in ParaView, they become available in ParaView, similar to