Fix order of joint_addrs if joint_names isn't none

[wesleymth]

• Bugfix: output lists of self.get_joint_pos_addrs(jntadr) & self.get_joint_dyn_addrs(jntadr) were missing a reverse
• Now if joint_names is specified, addresses of each joint are added to self.joint_pos_addrs & self.joint_dyn_addrs in the right order
• Bug: get_joint_dyn_addrs expects a motor associated to joint to get the correct addresses, therefore new get_joint_vel_addrs was added to address this issue