Draft: Adjust the size in FieldInfo automatically

Summary

The Dune::VTK::FieldInfo got a new Type value: none. This reflects that the data is neither a scalar, vector nor tensor, and should be written to the file with the number of components as specified in the FieldInfo. All other types are automatically adjusted to size 1, 3, or 9 for scalar, vector, or tensor, respectively. This is a hard requirement for the visualization in Paraview.

The value FieldInfo::size represents the number of components to write, not the number of components the grid-function/vtk-function range contains. This is a different interpretation to before. It is now required that the range is either a scalar or has a .size() method representing the number of range components.

Possibly breaking change

Note that before, a scalar Type had the documentation that it "may also be multi-component". This is changed in favor of a new Type called none. An alternative would be to adjust the size only for vector and tensor Type and do not introduce the none type.

This MR is related to the discussion in !702 (merged)