More tests

[sebmestrallet]

I've created tests/main.cpp to check if the incremental stats computation (include/stats.h) was accurate.

Later I added tests for the Geogram halfedges API that I extended (include/geometry_halfedges.h).

There are still no tests for labeling-related functions:

• initial labeling generation : naive, graphcut. See include/labeling_generators.h
• labeling graph construction, including turning-points identification. See include/labeling_graph.h
• elementary labeling functions. See include/labeling.h
• labeling operators. See include/labeling_operators_on_invalidity.h and include/labeling_operators_on_distortion.h
• export to the glTF format. See include/io_glTF.h

Other things not tested:

• geometry-related functions. See include/geometry.h
• macros & functions for containers. See include/containers_macros.h, include/containers_std.h and include/containers_Geogram.h
• Scaled Jacobian computation. See include/geometry_hexahedra.h
• distortion computations. See include/geometry_distortion.h and Ensure correctness of polycube_distortion #21
• conversion of PolyCut outputs. See app/convert_labeled_obj.cpp