Move 'AssertHelpers.hpp' to parent folder.
Simplify Deriche filter implementation.
Make asserts more generic.
Add more unit tests for Deriche filters.
Merge branch 'fix-image-processing-module' of github.com:DO-CV/DO-CV into fix-image-processing-module

Conflicts:
	src/DO/ImageProcessing/Deriche.hpp
Fix specialized `PixelTraits` class.