Walking on Bladors

It's far from being done, but at least now I can give it a try: I can start walking when standing on a blador. Issues remain:

• [done] once moving on a blador, I cannot stop: I slide. That's because "onpath" so far short-circuits "stopper" who was in charge of both bringing Bilou (with some inertia) to stop and check whether he'll fall. These two will have to be split for "onpath" to work properly.
• [done] I am not detached when I leave the blador, making me slide even when I walking *past* the blador. 
• [done] if bladors are stacked onto each other, make the upper one fall when the lower recovers.
• [done] same if the lower got picked up.
• [check] I may still end up not on the platform, but still forbidden to fall. Repelled and not attached am I ?
• [todo] Why is there a slight bounce when I'm done picking a blador ?
• [todo] horizontal speed killed when landing on a blador. But at least we can nicely move *out* of a blador.
• [done] Why am I able to "restore" a blador when I pick up the one he's standing on with random chance ?
• [todo] whatever went wrong with Bilou vs Inkjets ... fix it.