Clean and rework meshing code

[servantftechnicolor]

This PR is making a first step toward a more readable meshing code

• Removing dead branches
• Removing old options and conditions which are never used
• Creating multiple classes instead of the monolithic DelaunayGraphCut class :

1. PointCloud class for creating point cloud from sfmData or depthmaps
2. Tetrahedralization class for everything related to delauny cells management
3. GraphFilling class for Filling the graphcut and binarize the problem
4. Mesher class to postprocess the binary graph and generate the mesh