Add an option to draw a simplified version of the morphology

[marwan-abdellah]

To be able to load complex morphologies and also for the sake of exploring the connectivity aspects between the different branches of the morphology, we need to add an option to draw only the terminal samples of the morphology.

[marwan-abdellah]

To avoid elemenating the loops, we should use a three-point representation per section, unless the section has only two samples.