1) The Eigen package defines operator<< for Eigen tensors, but this format is different, hence Grid::Serializable::WriteMember
2) For simplification, the contents are written in memory order. I.e. Different results will be obtained depending on whether the tensor is row- or column-major
E.g. assuming T::rank is an int, then objects defined like so:
const auto rank{T::rank};
should also be int. Unfortunately, Intel '17 instead defines them to be std::initializer_list<int>, then proceeds to complain where these variables are used that they cannot be converted to int. NB: This was fixed under Intel '18
