Make sure ARE is working in Gazebo simulation

[traversaro]

Several users are experiencing issues that (I think) are related to not properly tuned joint-level PID position loops of the iCub model in Gazebo, see:

• [icub + Gazebo] icub_with_hands model not being "stiff" community#155
• unstable iCub behaviour when running ARE in Gazebo robotology-legacy/icub-gazebo-legacy#37
• icub_with_hands gazebo model joint6(wrist_yaw) position cannot be moved using yarpmotorgui robotology-legacy/icub-gazebo-legacy#35
• running iKinCartesianSolver with gazebo robotology-legacy/icub-gazebo-legacy#31

We should tune the position gains with respect to some clearly defined scenario, such as the ARE one described by @frank-foerster in robotology-legacy/icub-gazebo-legacy#37 . For reference we should document on which scenario we tuned the gains, such that in the future we can simplify the process of re-tuning the gains for different robots (such as R1).

[traversaro]

Renamed the issue after the recent findings.

[randaz81]

There's a bunch of bugs that prevent ARE from working in gazebo. I'll remove this message when the fixes will be pushed.

[traversaro]

Is this still the case @pattacini ? In any case, I think the proper place for this issue is icub-models.

[pattacini]

Most of the basic components of ARE (Cartesian Controller, Gaze Controller, hand controller) are working nicely now as demonstrated in https://github.com/robotology/icub-gazebo-grasping-sandbox.

Never tested ARE per se though.

[pattacini]

In particular, I've never checked whether WBD can run just fine.