Fix url of cmake sub-module
Merge pull request #1 from fvalenza/master

Fix url of cmake sub-module
Merge branch 'master' of https://github.com/humanoid-path-planner/hpp-constraints
DifferentiableFunction_t -> DifferentiableFunction.
Make constructors public in all constraint classes.
Use Eigen::Ref for Jacobian matrices.
Add setter and getter for reference values of RelativePosition.
Implement constraint on relative transformation between two joints.
Merge branch 'master' of https://github.com/florent-lamiraux/hpp-constraints
Add selection mask for Orientation and RelativeOrientation constraints

  - mask is a vector of 3 boolean value specifying which component of the
    error vector are constrained to 0.
Merge branch 'master' of https://github.com/humanoid-path-planner/hpp-constraints