Added some CMake macros to support discovery of Python modules.

Added a CMake file with two macros that support finding Python
modules on the system in a slightly more efficient way.  One of the
goals is that hereafter we will only need to run the external Python
process once for each module we need to test, and we will cache the
results so that subsequent checks can avoid the additional overhead.

There were two CMakeLists.txt where we were checking for the presence
of matplotlib, and these have been changed to demonstrate how the new
macros will be used.  As soon as these changes are accepted into VTK,
we would like to start using them in a similar fashion from the
paraview web testing framework.

Change-Id: I5439b10a4d8c0f8dc0b4209bbd429b104ef7c9c2
Enhanced the parallel coordinates chart for doubles

The parallel coordinates did not correctly handle double precision
input, added support to vtkPlotParallelCoordinates and created a
new test to verify it. Also some very minor clean up in the other
test, and fixed variable naming for consistency.

Change-Id: I4d688857dcfe86b044b8284789e7873f698d8820
Clean up coding style, use vtkNew instead of VTK_CREATE

Cleaned up the coding style used in the testing classes to be more
consistent, removed VTK_CREATE and replaced with vtkNew. Use the
std::string comparisons instead of strcmp.

Change-Id: Id6609b5072a632e1dc65fa5618872add5c38546b
If the original file is missing, make it non-fatal

The external data code makes it hard to add a new test as the test
is used to generate the baseline. Make the missing original a status
message rather than a fatal error. This allows you to add a new test,
compile it, generate the baseline and then add it as we did before the
move the external data.

Change-Id: I7cf25270c59ec1055c9e4c37d9e328f9f696f236
COMP: Help IBM XL compiler lookup vtkSMPTools_Impl_For

Fully qualify the name to disable argument dependent lookup and tell the
compiler exactly where to find the name.

Change-Id: Ibc58730d9ccf879a8cbdce47e08610ef6a0d7e6c
Merge topic 'vtkSMPTools-XL' into master

65a6d829 COMP: Help IBM XL compiler lookup vtkSMPTools_Impl_For
Merge topic 'render-test' into master

32e48028 If the original file is missing, make it non-fatal
592643f7 Clean up coding style, use vtkNew instead of VTK_CREATE
Merge topic 'parallel-coords-double' into master

347fb125 Enhanced the parallel coordinates chart for doubles
Merge topic 'cmake-python-modules-check' into master

658b5bbb Added some CMake macros to support discovery of Python modules.
ENH: Update more Filters/Core to support DesiredOutputPrecision

This updates a second batch of core filters to support a choice of
desired precision (default, single, or double) for output points. It
uses the analogous code in vtkThreshold as a model.

Change-Id: I404c1bf2ea624e9065768297a1ec5247d1751647