[WIP][constraint] adds JointConstraint

[EulalieCoevoet]

Thank you @TanguyNav for this work!

Proposition of changes:

• Instead of maxPositiveDisp / maxNegativeDisp, I would prefer using maxDisplacement / minDisplacement. When we want a positive minimum it's really weird to give a negative value. Even in the general case I find it confusing (I don't like it either in CableConstraint...).
• For me the references to both displacement and angle are confusing. It's true that the joint does not have to be angular and could be a linear displacement. I would remove all the references to angle.
• From a user point of view (from the python script) we use the data names value and valueType in the other constraints (CableConstraint, SurfacePressureConstraint, PositionConstraint). I would prefer to keep it uniform and thus avoid using imposedValue instead of value.