Refactor Edge class and derived classes

  -> generateTargetConfigOnLeaf.

  - reference ICRA 2017 paper.

  Make previous methods deprecated
  Rename Graph::configConstraint(EdgePtr_t) into targetConstraint.

  remove unexisting input.

  make old methods deprecated.
  This will homogeneize with hpp-manipulation-corba naming.

ManipulationPlanner calls the problem PathValidation instead of the e…

Handle security margin for pairs of bodies.

  - Implement method GraphPathValidation::setSecurityMargins.
  - Add method Edge::securityMarginForPair to set a security margin for
    a pair of joints along an edge.

[Edge] replace methods from and to by stateFrom and stateTo

  from is a python keyword. This is an issue when using python bindings.

Add steering method EndEffectorTrajectory

Add cost in GraphComponent.

[steeringMethod::Graph] If q1 == q2, call problem inner steering method.

Improve graph validation + fix dynamic cast issue.