Implement continuous collision checking.

  For each pair body - body and body - obstacle, create an object of class
  BodyPairCollision that computes the maximal velocity of all points of a
  body in the reference frame of the other body.

  Using those objects, validate the interval of definition for each pair or
  detect a collision.
Fix bug in compuation of forward kinematics.
Define a typedef for list of BodyPairCollision.
Implement tolerance in ContinuousCollisionChecking

  - At the end of interval validation, remove the part relative to penetration
    for each pair.
Fix bug when maximal velocity is equal to zero.
Implement collision and distance computation with environment outside Device

  Add class CollisionValidation for collision,
  add class DistanceBetweenObjects for distance computation.
Rename ContinuousCollisionChecking -> continuousCollisionChecking::Dichotomy.
Implement progressive continuous collision checking.
Apply addObstacle method to each ConfigValidation object

  - in ConfigValidations.
Move BodyPairCollisions_t in namespaces.
Use a typedef for std::list <BodyPairCollisionPtr_t>.
Add RemoveObstacleFromJoint in classes dealing with collision.
Use list instead of vectors to store objects.
Set penetration to 0.025.
Implement other algorithm for continuous collision detection.
Remove debug ouput.
Re-implement continuous collision checking

  - do not allow penetration anymore. tolerance_ now stands for the acceptable
    distance to collision of the end of the valid sub-path.
Reimplement progressive continuous collision checking.

  Evaluate collision between pairs at increasing sequence of parameters along
  path (if not reverse).
  Next parameter is computed in such a way that no point has moved by more
  than twice the penetration. If collision extract path between start and last
  validated configuration.
Update Dichotomy continuous collision checking algo to version of commit 5f3966

  - this version revelead the best one for non-constrained problem and without
    penetration allowed.
Use one BodyPairCollision by joint

  - although it would seem more efficient to use different pairs for different
    obstacles, it is not.