Completely overhauled the PVGPpy module to be ready for the transition to using `VTKPythonAlgorithmBase` subclasses outlined in [Merge Request !2516](https://gitlab.kitware.com/paraview/paraview/merge_requests/2516/) for ParaView.
We will be phasing out the `src` directory and XML build scripts on the `rebuild-pvpy` branch moving forward.
By using `VTKPythonAlgorithmBase` subclasses moving forward, we can deliver a single Python module that can be used both as a standalone package in Python environments or imported to ParaView to harness plugins from the Graphical User Interface.
**Proceed with caution until next minor release: *0.8.0***