Rename M_PI and to DART_PI (and other similar cases), add Log() for Isometry3d and Matrix3d.
Remove xformHom and xformHomDir that take Eigen::Matrix4d because we use Eigen::Isometry3d instead of Eigen::Matrix4d to represent transformation.
Use Eigen::Isometry3d::inverse() instead of dart::math::Inv(). Eigen::Isometry3d::inverse() perform as much as dart::math::Inv(). See: http://forum.kde.org/viewtopic.php?f=74&t=108512
Clean up euler-angles related part of math.