Fix cubical complex functions

[JacquesOlivierLachaud]

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PR Description

This PR fixes two issues related to CubicalComplexFunctions: issue #1362 and issue #1381 (for progrmas testCubicalComplex, testVoxelComplex and testParDirCollapse).

Checklist

• Unit-test of your feature with Catch.
• Doxygen documentation of the code completed (classes, methods, types, members...)
• Documentation module page added or updated.
• New entry in the ChangeLog.md added.
• No warning raised in Debug cmake mode (otherwise, Travis C.I. will fail).
• All continuous integration tests pass (Travis & appveyor)

[rolanddenis]

Thx !

Can you also remove the using namespace ::DGtal::functions; of CubicalComplex::link, and fix the indentation (mixed tabs and spaces) of CubicalComplexFunctions.ih?

[phcerdan]

Should the two operators in VoxelComplex also be moved out of the namespace?

DGtal/src/DGtal/topology/VoxelComplex.h

Lines 50 to 63 in 33db467

	// Forward definitions.
	template <typename TKSpace, typename TCellContainer>
	class VoxelComplex;
	namespace functions {
	template <typename TKSpace, typename TCellContainer>
	VoxelComplex<TKSpace, TCellContainer> &
	operator-=(VoxelComplex<TKSpace, TCellContainer> &,
	const VoxelComplex<TKSpace, TCellContainer> &);
	template <typename TKSpace, typename TCellContainer>
	VoxelComplex<TKSpace, TCellContainer>
	operator-(const VoxelComplex<TKSpace, TCellContainer> &,
	const VoxelComplex<TKSpace, TCellContainer> &);
	} // namespace functions

I can do it as well in other branch after this gets merged.

[rolanddenis]

Yes, I think we could have the same compilation issues with VoxelComplex. Please do so 🙏

[JacquesOlivierLachaud]

So we merge and Pablo fixes VoxelComplex operators in another PR ?

[rolanddenis]

Yep, mergin... Thanks for the PR!