RelativeTransformation -> RelativeTransformationSE3 with mask.

  - methods formerly taking a const reference to Problem as input now take
    a shared pointer to const Problem.

  Set error threshold for each internal edge to the value of the edge divided
  by the number of internal edges.

  -> generateTargetConfigOnLeaf.

  - reference ICRA 2017 paper.

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

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

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

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