[C++][unittest] Fix computations in jointcomposite::calc() + reworked unittest (comparison of R3xSO3 (either two joints with no inertia between them or Jointcomposite))

Added methods in joints and algorithm working on Model to determine if two configurations are equivalent

There are still some bugs inside differentiate, interpolate

[C++][unittest] Added neutralConfiguration vector in Model, and fill it when adding joints + test on neutralConfiguration

[C++] bodies are now a subpart of the Frames : some Frames are of type BODY and when referring to getBodyId/Name in Model it will look in its frames

[C++] Make distinction between joint and body in Model API ( addJoint, appendBodyToJoint, addJointAndBody instead of addBody)

[C++][Doc] Removed random. Changed uniformySample into randomConfiguration + Updated doc of joint-configuration algorithms. + reindentation

[C++][Python] Added a new macro for algorithms that work only with joint models instead of joint models and joint datas. Modified python binding and API accordingly

[C++][Python] Added algorithm working with joint configurations ( integrate, differentiate, interpolate, random, uniformlySample, distance), their python bindings and unittest