Use Eigen::Transformations instead of straight matrices

[saulrh]

http://eigen.tuxfamily.org/dox/classEigen_1_1Transform.html - static typing may be more efficient? May also useful functions for converting to other representations (quaternion, euler, etcetera).

[cerdogan]

What is the difference between Matrix4d and a Transform? Both are staticly typed right? Also, did you do a timing comparison between the two?