Generalized constraints

[Ipuch]

class Constraints:
     class ConstantDistance:

               def    constraint()
               def    cosntraint_jacobian()


     class ConstantAngle:

Issue unclear, but I feel like there are only two types of constraints constant length (with either zero distance) or constant angle (mostly perpendicular). This could be implemented somewhere for more abstraction. Thus, the jacobians are also the same.