Adding visualizers

[CarlottaSartore]

This PR adds:

• Mujoco visualizer
• iDynTree visualizer

[CarlottaSartore]

Still a draft I have to modify the documentation and add examples.
But I have used the visualizers for other applications and they worked

C.C. @flferretti @diegoferigo

[DanielePucci]

@CarlottaSartore I was thinking how much effort would it be to add also our logging-and-visualisation infrastructure that as soon as gbionics/bipedal-locomotion-framework#796 is close is also enabled for real-time visualisation

[CarlottaSartore]

@CarlottaSartore I was thinking how much effort would it be to add also our logging-and-visualisation infrastructure that as soon as gbionics/bipedal-locomotion-framework#796 is close is also enabled for real-time visualisation

I was checking with @GiulioRomualdi and it seems it would need yarp server running, which is currently not a dependency on comodo.

Since it is needed for visualization (which is not intended to be used in parallel ) we can think of adding this visualizer, and making the dependency on yarp not compulsory.

Despite this, I do not think it will be difficult

[traversaro]

The main problem I think there is "how to start programmatically robot-log-visualizer?". For what regards dependencies, on Python I think it is possible to do lazy loading, so probably it is not a big problem.