Change the naming of JogJoint and JogFrame messages

[7675t]

I want to make these messages public after naming reasonably. Please give me some opitnion if you have @534o

• JogJoint.msg
  • name should be joints, I thought.
  • displacement is a little abstract, so I think to use delta to clarify the displacement is differential
  • And should we make it plural? Some ROS message is confused on it (JointState.position and JointTrajectoryPoint.positions)
• JogFrame.msg
  • linear and angular seem to be abstract, so I think to use linear_delta and angular_delta

[7675t]

I've changed mind a bit. joints is still ambiguous, joint_names would be ok.