[WIP] Change curvature estimation for keypts extraction

• By now, the curvature estimation uses line fitting on left and right laser ring neighbors of each point.
• The angle between these lines and the depth gap between the studied point and these neighborhoods are analyzed.
• With this MR, the curvature is estimated as in LOAM algorithm with a convolution. A kernel (1 1 ... -N 1 1 ) of size N+1 is applied on points' neighborhood.
• This solution permits to achieve comparable results on common datasets relatively to previous version. However, results on forest-walking datasets are not as good as with previous version (see picture below, left : LOAM based, right : master result).
• Some results on keypoints extraction are saved here for more info

Results not so good and the extractor has been improved.