Add computation of body radius

  The radius of a body is an upper bound of the maximum distance between the
  points of the body and the origin of the joint.
Fix compilation error with gcc-4.6.3

  Constructor of vector with (0) as input has misteriously become ambiguous.
Add Specialized joint type in fwd.hh
Update cmake sub-module.
Cosmetic change: fix doxygen documentation

  - notify copyright outside doxygen,
  - remove obsolete tags.
Add missing "inline" in configuration.hh.
Simplify integration on angular velocity from quaternion.
Try to keep norm of quaternion close to zero when integrating.
Rename private method

  Joint::computePosition -> Joint::recursiveComputePosition.
Make Joint::computePosition public and provide reference to result as parameter.
Merge branch 'master' of https://github.com/humanoid-path-planner/hpp-model