Draft: integral_constant return type for FieldVector/FieldMatrix size methods
As mentioned in !1289 a generic implementation of matrix methods changing the matrix size is currently not possible. The main reason is that there is no way to create a unified constructor/creator interface.
This MR modifies the size/dim/mat_rows/mat_cols/...
methods to return std::integral_constant
so that it is (in principal) now possible to write a creator for FieldMatrix/FieldVector
, which gets the size as function parameters and not (directly) as template parameters.