Added VTKPythonAlgorithmBase - base class for Python algorithms.

VTKPythonAlgorithmBase can be subclassed to create Python
algorithm classes that can be directly inserted into the
pipeline.

Change-Id: I3a575a8b8c20aa79d1854950ab5f383e80bca548
Merge topic 'new-python-algorithm-base' into master

f5af80dc Added VTKPythonAlgorithmBase - base class for Python algorithms.