Provide a method to set the sample spacing for slab modes.

The slab modes of vtkImageReslice allow for "thick slab" views, where
several slices are combined, for example, to create a maximum intensity
projection.  Previously the spacing between these slices was always set
to the output slice spacing, which was fine if the user only wanted to
create a single "thick slab", but less useful if the user wanted to create
a series of "thick slabs".  This patch adds a new method, called
SetSlabSpacingFraction, so that the user can first set the OutputSpacing
to set the spacing between the output slabs, and can then set the
SlabSpacingFraction to set the spacing between the slices that are
combined to make those slabs.

Change-Id: Ib70e92da9b1e27ba59a7a293d6e19b51ac25c9bb
Changed the default CDash URL for VTK

The CDash instance was moved to open.cdash.org some time ago, update
out configuration to reflect its current location.

Change-Id: Ic1a897339571bafebbabbecbeb1e73814d1acf6e
Move several TEST_DEPENDS to switch on backend

These tests should work with either backend, and were inadvertently
merged with a hard dependency on OpenGL2 backend.

Change-Id: I25356b499d2317143db37e3fa59b04c5b1c53710
Merge topic 'rendering-backend-tests' into master

e96a36cf Move several TEST_DEPENDS to switch on backend
Merge topic 'cdash-url' into master

703b6d91 Changed the default CDash URL for VTK
Create object factory CMake file, move vtk_add_override

This macro is copy/pasted to several files, more of the functionality
should be moved soon too.

Change-Id: If29eb8eec07508aa591758483be3dd189fe1cca8
Now generate the object factory files in a function

This moves the logic for object factory override generation to a
central function, and removes lots of copy/paste code in our CMake.
Also removed/retired the OpenGL2 object factory stomping variation
as it is no longer needed and could produce unwanted side effects.

Change-Id: I4a5ee2db76f73d57eded1d9a9240cefc4918cd74
Revert "updated baseline images"

This reverts commit 1f36e41fb06ebfb77f2b8e7f93bf147907792684.

Change-Id: I4462cdfddb9fd83b49fa4333b7fe81aa202f4464
Revert "updated baseline image"

This reverts commit 0fe4c062419f4494f66736843c8fe2c84f767816.

Change-Id: I389e9ae11b6918801fe557872d91247681877b74
Some dependency updates now vtkRenderingContext2D is abstract

This adds dependencies to tests that were missed in the initial move
for vtkRenderingContext2D.

Change-Id: If816a2a15ca02bca8c5f736872d4166b90f73bcf
Merge topic 'refactor-object-factory-cmake' into master

cc8d1471 Now generate the object factory files in a function
7def3bbc Create object factory CMake file, move vtk_add_override
Don't exclude the module from wrapping - initialization

I am not sure if this is the correct solution, but it matches what
we do for vtkRenderingOpenGL, etc. There is little point in us
wrapping these classes, but we want the relevant implementation
module to be linked/initialized by the wrapped language in order
to be able to render charts correctly using a concrete
implementation.

Change-Id: I2402b3578f5a89b10dad2619c955e900c7ab822b
Made the label tests pass again!

They were moved from vtkRenderingOpenGL, and they obviously relied
on the vtkRenderingFreeTypeOpenGL overrides to produce the expected
baseline image.

Change-Id: Ic6b33f314a308204a2125d5bc84f3ca056b76b9b
Make TCL wrapping happy - no numbers in module names

Change-Id: I3473b62db345c5cf51233578d72b4e3f6de26342
Merge topic 'test-baselines' into master

a550da34 Make TCL wrapping happy - no numbers in module names
c3ea64b9 Made the label tests pass again!
3d17f6c0 Don't exclude the module from wrapping - initialization
e7f01404 Some dependency updates now vtkRenderingContext2D is abstract
66f4884e Revert "updated baseline image"
5766bc89 Revert "updated baseline images"
Added include for std::string

Change-Id: I125b625e936e90d1682019c183b397baada751ed
Merge topic 'string-abstract-render' into master

ce2fbc55 Added include for std::string
mpi4py: link to CMAKE_DL_LIBS

Required on one of the dashboards at least.

Change-Id: I96d2ddb5351ef8d5c9d9f3ced52c74cac82d9d4d
Merge topic 'mpi4py-dlopen-link' into master

1493ff0c mpi4py: link to CMAKE_DL_LIBS
Fixing array bounds issue

When alpha is zero, the array is indexed past the end.
This junk data is then multiplied by zero so it had
the correct behavior on most platforms, but for some
(e.g. Visual Studio) there is runtime bounds checking
and the program would error. So check for this case
to avoid going past the end of the array

Change-Id: I0d1c8bf94a65983fd8303ffbb7e1c75ca778f614