Duplicate conversion functions in eigen_helpers.hpp

[dmcconachie]

There are extra conversion functions for some types of objects. These should be resolved at least to the point of having one call the other.

[dmcconachie]

inline std::vector<double> EigenVectorXdToStdVectorDouble(const Eigen::VectorXd& eigen_vector)

template<typename T>
inline std::vector<T> EigenVectorXToStdVector(const Eigen::Matrix<T, Eigen::Dynamic, 1>& eig_vec)