[Gazebo] Add (but commented) the pid parameters for the position controller

[ipa-nhg]

Currently the Gazebo simulation, although everything is working perfectly, pops up the following erros/warnings:

[ERROR] [1562314333.213958955, 0.341000000]: GazeboRosControlPlugin missing <legacyModeNS> while using DefaultRobotHWSim, defaults to true.
This setting assumes you have an old package with an old implementation of DefaultRobotHWSim, where the robotNamespace is disregarded and absolute paths are used instead.
If you do not want to fix this issue in an old package just set <legacyModeNS> to true.

[ERROR] [1562314333.328514271, 0.341000000]: No p gain specified for pid.  Namespace: /gazebo_ros_control/pid_gains/shoulder_pan_joint
[ERROR] [1562314333.329583042, 0.341000000]: No p gain specified for pid.  Namespace: /gazebo_ros_control/pid_gains/shoulder_lift_joint
[ERROR] [1562314333.330642618, 0.341000000]: No p gain specified for pid.  Namespace: /gazebo_ros_control/pid_gains/elbow_joint
[ERROR] [1562314333.331618601, 0.341000000]: No p gain specified for pid.  Namespace: /gazebo_ros_control/pid_gains/wrist_1_joint
[ERROR] [1562314333.332616502, 0.341000000]: No p gain specified for pid.  Namespace: /gazebo_ros_control/pid_gains/wrist_2_joint
[ERROR] [1562314333.333662371, 0.341000000]: No p gain specified for pid.  Namespace: /gazebo_ros_control/pid_gains/wrist_3_joint

[ WARN] [1562314333.341661101, 0.342000000]: The default_robot_hw_sim plugin is using the Joint::SetPosition method without preserving the link velocity.
[ WARN] [1562314333.341687900, 0.342000000]: As a result, gravity will not be simulated correctly for your model.
[ WARN] [1562314333.341706822, 0.342000000]: Please set gazebo_pid parameters, switch to the VelocityJointInterface or EffortJointInterface, or upgrade to Gazebo 9.
[ WARN] [1562314333.341727976, 0.342000000]: For details, see https://github.com/ros-simulation/gazebo_ros_pkgs/issues/612

The first error is fixed by this PR. Unfortunately set of the pid gains for the position controller just break the arm and the controllers are not working at all. I tried implementing an EffortJointInterface (instead of position) but this is also not working.

Although gazebo shows errors the controllers are working, then I suggest to keep the lines but commented. Probably are useful in the future.

(PID parameters taken from ur_moder_driver configuration e.g. https://github.com/ros-industrial/ur_modern_driver/blob/master/config/ur10_controllers.yaml#L76-L83 I tried also tunning them with the dynamic_reconfigure, I didn't find a combination that works)

[ipa-nhg]

Related to: #386

[gavanderhoorn]

Note: if we do switch to effort interfaces (#521), this PR will not be needed any more.

It would still be relevant for kinetic-devel, as that branch will not see any of the updates in #448.

[ipa-nhg]

out-of-date and (kind of) superseded by: #525

I think it can be closed, at the end this status is not solving the issue neither for kinetic, the PR was open to have the issue with the PID for gazebo documented and with the hope that a gazebo update solved the problem.