replaced ? by if in sphere_sphere distance for compilation purposes

  If GJK::evaluate fails to converge but that the distance of the origin to the
  simplex converges to 0, set distance and return fail. In shapeDistance,
  return collision if GJK::evaluate failed.

  This test makes GJK fail, reaching the maximal number of iterations.

  - if dir [2] == 0, return a point with z coordinate equal to 0,
  - add a test between box and cylinder that did make GJK algorithm fail.

  Methods BVTesting with sqrDistLowerBound as output argument were not defined.
  Instead the implementation of the base class BVHCollisionTraversalNode <BV>
  was called instead. Unfortunately, in the base class, the meshes and
  bounding volume hierarchy were moved to the position given for collision
  testing, but not in the derived classes. Method overlap were then called with
  wrong argument for position and orientation.

  distance lower bound is necessary to compute security margin. In the previous
  state of the code, security margin was not computed if distance lower bound
  was not selected.

  - This member is used to convert a octomap to a set of boxes.

  This test was malformed. It tested collision for tangent shapes and checked
  that A against B and B against A were collision free.

  - many tests put shapes in singular configuration so that normal and depth
    are ill-defined. This modifications removes tests that are not relevant.

  in a local header so that they can be called from another file.

  from BVHCollisionTraversalNode::leafTesting to
  GJKSolver_indep::shapeDistance<TriangleP, TriangleP>.

  - do not run EPA algorithm to compute penetration depth and normal.

  - Collision detection calls distance computation and returns collision
    if the distance between objects is below the security margin.
  - This modification requires a modification in the structure of the software
    to make collision detection and distance computation closer.
  - GJKSolver_indep::shapeTriangleDistance and
    GJKSolver_indep::shapeTriangleIntersect have been replaced by
    GJKSolver_indep::shapeTriangleInteraction.

  - this member stores the normal (direction object 2 should be translated by
    the penetration depth to make objects collision free) in case boths objects
    are in collision.