Adaptation of the Joint Base Class to integrate parent_point and child_point (eventually ?)

[ANaaim]

After the #85 the following was discussed :

"Super" calls the parent class JointBase that has common entries for every joint. As all joints doesn't have a parent and child point yet.
It's not relevant to initialize them now. But this would be a great idea in the future !
Then, to initialize parent and child point with proximal and distal point would be automated for every joint, in the parent class JointBase to avoid redundancy.

[Ipuch]

It requires to generalized hinge and universal joints to any application point, once its done this issue would be relevant and a good first issue !