Reorganize path validation + fix SplineGradientBased

  Initially only the create method was template. Now the constructor, hence the
  class has to be template,
  When adding a constraint, do not perform collision test again on configuration
  in collision, use collision report to get objects in collision and contact
  points.

Because it's faster than collisionValidation

that occured when p1 == p2 and v1 != v2

Check if given parameters and end configuration are consistant