BUG: Fix alpha assignment for RGBA TIFF.

The alpha value should not be inverted.

Add additional test file baseline for regression testing.

Co-authored-by: Мар'ян Климов <nekto1989@gmail.com>
Co-authored-by: Ivan Kubarev <Ivan.Kubarev@materialise.kiev.ua>

Change-Id: Ic865abb18fe11739df0633888423a4b302efc2ec
ENH: Importing Laplacian Deformation for QuadEdgeMesh

Code from IJ paper Laplacian Mesh Deformation

  http://www.insight-journal.org/browse/publication/890
  http://hdl.handle.net/10380/3410

Change-Id: I170de75843605e51f79f59db04d5f3c6db24f111
DOC: Add more explanation about SmoothingQuadEdgeMeshFilter's usage

Change-Id: I23e501b89d96ef24fb0effe97a1c517f9b3deeed
ENH: Do not setup the python tests if not asked

When building with python wrappings, the test files were downloaded and the tests were setup.
This is now done only if asked by the user, by setting BUILD_TESTING to ON

Change-Id: I81e711fb696083afc715d15ee0a3e1511ba91a41
Merge topic 'DocSmoothing'

48cade29 DOC: Add more explanation about SmoothingQuadEdgeMeshFilter's usage
Merge topic 'RGBATiff'

86f19dd7 BUG: Fix alpha assignment for RGBA TIFF.
BUG: Improve thread-safety and performance of PCAShapeSignedDistanceFunction.

m_Selectors is a smart pointer, and if manipulated by multiple threads, there
can be race conditions to set its value.  Through some refactoring, this
member variable is no longer needed and is removed.

Change-Id: I762dd7751e7ebfab39f77f11b1cd3ab653c69c04
Merge topic 'PCAShapeSignedDistanceFunction_release'

ffa8ff76 BUG: Improve thread-safety and performance of PCAShapeSignedDistanceFunction.
DOC: itk::statistics -> itk::Statistics.

Change-Id: I3ea191ae4fa87fb076346f4c481cc4324acc9481
DOC: Remove duplicate text in LaplacianRecursiveGaussian example.

This appears to be a copy/paste error from the
SmoothingRecursiveGaussianImageFilter.

Change-Id: I81dd7ccd6b563495a7521bce722036169d994aa1
DOC: Fix Software Guide page overruns in IterativeClosestPoint{1,2}.cxx.

Split up the literal code section.

Change-Id: I921913032ce143c413ba734c77af8ad5dd6cc4d0
Merge commit 'dfc724c3f31150ff76f11ebdca53a232fb' into release

Change-Id: I7ea69e64d6c51413929408f55b360601281b3486
Merge branch 'release'

Change-Id: I58f527220e8fb6705dae9bb1bba3ba57d3bf77ec
Merge topic 'PythonTests'

4dd827dd ENH: Do not setup the python tests if not asked
Merge topic 'LaplacianDeformation'

6c86b9f1 ENH: Importing Laplacian Deformation for QuadEdgeMesh