These Python tests have been refactored.

This has been done by removing the "tcl-isms" and making
 the code more readable. In some cases redundant code
 has been removed (often a result of copy/paste operations).
 The code has also been checked to ensure each line is 80
 characters or less.

The code can now be run using vtkpython or by using the
 appropriate Python environment.

Originally these were TCL scripts that were converted using
  vtkTclTestToPy.py and they they needed to be run through the
  rtImageTest.py driver which defines a few needed
  functions/variables for their operation. To this end
  backdrop.py has been added where it is needed.

Change-Id: I50d6505628c140ea4551f74f7f3e85df907567e1
Signed-off-by: Andrew Maclean <andrew.amaclean@gmail.com>
Export vtkgl::LoadExtension and vtkgl::GLVersionExtensionsString.

Change-Id: Icdbbab8ba7c00dc739dff43449583ac9ac74d1ba
Merge topic 'RefactorPythonTests' into master

3810c5a6 These Python tests have been refactored.
Merge topic 'export_vtkgl_LoadExtension' into master

09db49da Export vtkgl::LoadExtension and vtkgl::GLVersionExtensionsString.
Added new class to warp a vtkPointSet using MVC interpolation

This class uses Mean Value Coordinate interpolation to warp an
underlying vtkPointSet (e.g., vtkPolyData, etc.). It requires a
control mesh that is manipulated to effect the transformation.

Change-Id: If272bd9a3374acdb3b8b8e13e1fad346f6096694
Merge topic '13984_64bit_headers_for_xml_writers' into pv-master

9b1a0f4 Merge topic 'bug_2379' into master
444257e BUG #2379. Passing flags correctly to internal writers.
275e4b2 Merge topic 'chart-selection-modes' into master
840f0ee Merge topic 'matplotlib-warning-status' into master
6884e6d Merge topic 'scalarbar-leak' into master
cc42420 Fix for subclasses overriding EditAnnotations.
f82398a Introduced a new chart selection mode
d77d09c Merge topic 'imageproperty-test' into master
2465c99 Fix X BadRequest errors in TestInteractorStyleImageProperty.
9c18166 Merge topic 'fix-GRAMdetection-overflow-under-X' into master
3de8451 Merge topic 'remove-fast-numeric-conversion' into master
d72bb3c Merge topic 'garbage-collection-cleanup' into master
899403c Merge topic 'vtkFieldData_AddArray_add_documentation' into master
84c4260 Fix a leak revealed by ParaView; use SmartPointer.
853f854 Merge remote-tracking branch 'pvvtk/pv-master' into HEAD
a749623 Document the return value of vtkFieldData::AddArray().
...
Merge remote-tracking branch 'pvvtk/pv-master' into HEAD

* pvvtk/pv-master:

Change-Id: Ia9a41de49a2c810bcb7852afc58f1ec5032975c5
Refactoring code to set color/opacity/visibility for blocks.

This commit refactors some of the code added in recent weeks to add ability for
users to set display paramaters for blocks within a composite dataset. This
commit additionally adds support for changing block opacity.

Blocks colors/opacities can also be overridden when using scalar coloring.
The only issue is when depth-peeling gets used. In that case, point-data coloring
with texture (i.e. using interpolate scalars before mapping) results in color
bleeds. We need to dig into the depth peeling code to address that issue.

Change-Id: I2c86912b45bc0516dc4dc726df9448e0569c8312
Merge topic 'multi-block-color-support' into master

52fd8ad8 Refactoring code to set color/opacity/visibility for blocks.
Merge topic 'DeformPointSet' into master

1e7f2739 Added new class to warp a vtkPointSet using MVC interpolation
Provide information on plot input data range.

This commit provides an interface for querying the
range of values taken on by a vtkPlot's X- and Y-axis
inputs.

This can be used to determine whether log-scaling
is appropriate for each axis of the plot. It is part
of a fix to ParaView bug 13899.

Change-Id: Ia0449ca496dd935fb4ca25dc5dd2b691d2f89d93
Merge topic '13899_log_axis_warning' into master

6f8f8037 Provide information on plot input data range.