set limit(upper/lower), safety_controller(soft_upper/lower_limit, k_position) is optional
falling and raising in joint/calibration is optional, see http://wiki.ros.org/urdf/XML/joint
set optional for pr2 transmission, see http://wiki.ros.org/urdf/XML/joint
Merge pull request #53 from k-okada/hydro_devel_merge_47

Hydro devel merge 47