Orthognal vector code may be redundant

[dmcconachie]

eigen_helpers.hpp has the following functions:

template <typename DerivedV>
inline Eigen::Matrix<typename DerivedV::Scalar, Eigen::Dynamic, 1> GetArbitraryOrthogonalVector(
            const Eigen::MatrixBase<DerivedV>& vector);

template <typename DerivedV>
inline Eigen::Matrix<typename DerivedV::Scalar, Eigen::Dynamic, 1> GetArbitraryOrthogonalVectorToPlane(
            const Eigen::MatrixBase<DerivedV>& plane_vector1,
            const Eigen::MatrixBase<DerivedV>& plane_vector2,
            const Eigen::MatrixBase<DerivedV>& vector);

Eigen already has some functionality that may do this already, we should check that the functionality is not duplicated.

https://eigen.tuxfamily.org/dox/group__Geometry__Module.html#title53