Added utility function matplotlib_figure(width, height)

This saves on some boilerplate for setting up matplotlib figures in
Python views.

Removed some unneeded semicolons.

Change-Id: I1036d88eb979dff73aeb0c4c6ea855091e14ab7a
Added comparison against baseline for Python View test

Change-Id: Icd69b17bd9cdfd992bc19356301cf6717fa4d61e
Removed dependency of pqPythonView on matplotlib

It remains dependent on PARAVIEW_ENABLE_PYTHON being on.

Change-Id: Ia519c9bbf5a2ba559b8c62e6d79c065ccdde23e4
Added two Python View tests

One tests creation of a view image from a numpy array and the other
tests creation of an image using only VTK. Added baselines as well.

Change-Id: I03ce0abaa029ebbc8284712e3dde11f13a51865f