To achieve the maximal efficiency of traits approach is necessary to
change name type from std::string to const char*.
Moreover, I had to make the default trait public in another way. There
is a function creating and returning the generated Trait. At first sight
is seemed to me as bad idea, but the compiler can not work so
efficiently with it. Thus, it is better to have static function which
generates the object of traits.

Refactor

CSVDBG first test. Now i can represent only simple wariables.

documentation.

whether the varible is iterable and then writes the content of the
container.

Setup of boundary cells
Cells distace over face

I realized, that it would be better to implement methods working with mesh elements in the class UnstructuredMesh.
Finally, I managed to implement concept of unstructured mesh in any dimension.
Further work will be done after consultations.

Now the intent is clear and only few things like center points are to be implemented.
Then create wrappers for cells, faces etc.
Also is necessary to create methods for calculating lebesgue meassure.