Generate joint_limits.yaml using ordered joints

[JeremyZoss]

The joint_limits.yaml file is currently generated using a seemingly random joint ordering. This can lead to confusion, if users edit the file without checking the joint name field. Most users probably expect the joints to be listed in a sensible ordering: base->tip, alphabetically, matching URDF ordering, etc.

It would be nice to impose some sort of ordering, to minimize confusion.

[felix-kolbe]

+1 This would also avoid pointless changes in version control

[davetcoleman]

Done, your welcome ;-)