Added risk-analysis for simulation

[vvasco]

This PR introduces the risk-analysis folder, used to assess in simulation:

• the time to stop when detecting an obstacle;
• the time to completely stop;
• the impact force during a collision between R1 and a small box with a force torque sensor attached.

The risk-analysis folder includes:

• the gazebo worlds and models used to run the analysis;
• a scripts folder, including:
  • a python script to measure the safety times;
  • a bash script to measure the impact force;
  • matlab scripts to plot the results;
• a dockerfiles folder including a compose file used for the analysis.

How to run and the related results are described in the README.

We also added two gazebo plugins in the modules folder to evaluate the contacts and the forces.

[vvasco]

Addressed the comments, thanks @pattacini

[pattacini]

Once the CI is passed, I'll merge the PR.