Matrix transform tutorial update

If you want to see what the new version looks like:
http://vicopsp.free.fr/pcl_tutorials/matrix_transform.html#matrix-transform

Corrections:
  * Correct include (pcl::transformPointCloud)
  * Show how to use Eigen::Affine3f
  * Help about transforming points/vectors
  * Replaced tabs with spaces in source code
  * Updated source code with Eigen::Affine3f example