many improvements; discovered unwanted resize when deleting somas while window has been resized first

For the moment, more relevant results (biologically speaking) without dilatation/erosion.

EROSION/DILATATION during connexion: added possibility to choose between 2 erosion conditions. The strict one seems to be best (strict_erosion=True)

solved BIG BUG: tangency of extensions and connexions leading to "deskeletonization" and sklgraph incoherence with python objects