Use indoor flight data to rescale the COLMAP model
If the rescale is not enough, registration will have another rescale, be robust to the change of scale for the different throshold
in occlusion generation

* To do : use flight data to deduce model scale

 * fix README format problem
 * Change pcl util c++ programs to use c++ 14 instead of  c++11 (for PCL 1.10)

 * add videos splitting when they are too long
 * add already coputed groundtruth index
 * add point cloud densening by colmap
 * use matrix until the end instead of mlp files : thanks to this, the matrix can be modified manually with a custom point cloud registration