Fix compilation errors in interpolation function.
Fix compilation errors in scaling functions.
Fix compilation errors in differential operators.
Fix compilation errors in warp function.
Fix compilation errors in Deriche filtering.
Merge branch 'develop' into fix-image-processing-module
Merge branch 'develop' into fix-image-processing-module
Merge branch 'develop' into fix-image-processing-module
Merge branch 'develop' into fix-image-processing-module
Reactivate `ImageProcessing` module.
Clean up `UseDOImageProcessing.cmake`.
Remove support of precompiled header.

This is not an important feature and the support of this is way too
clunky.
Fix `UseDOImageProcessing.cmake` and a few minor things.
Add `PixelTraits` class to `Core` module for Deriche filters.
Use lower_case and underscores naming style and use `PixelTraits`.
Add stub unit tests for Deriche filter.
Remove inclusion of unversioned header.
Use exceptions and more intelligible variables.
Use pointer instead of iterator.
Move 'AssertHelpers.hpp' to parent folder.