Rename package fcl -> hpp-fcl

  Avoid conflict between fcl official version as installed by ROS and hpp
  modified version.
Fix bug in jointRotation::UnBounded::integrate
Add JOINT_POSITION in enum Computation_t.
Add mention to functions hpp::model::[integrate,difference]

  for a mysterious reason, the doxygen refuses to generate the documentation
  of those inline functions.
Cosmetic change

  Cut long lines.
Fix bug in rotationJoint::Unbounded::difference.