Creation of plugin to simulate magnetic forces

[jplayan]

Hello!

I'm a PhD student working on robotics within magnetic fields. I originally created an issue (#2849) mentioning that I had created a plugin to simulate magnetic forces.

I've already implemented some points and some others I would still like to add. I create this pull request to get feedback or for the main maintainers to give feedback on specific parts if they have time.

The main points I would like to implement are:

• Wrench induced in a ferromagnetic element when inside a magnetic field
• Magnetic field generated by a permanent magnet
• Allow loading a predefined magnetic filed (from a file such as a ".csv")
• Visualization of the wrench in each magnet

Let me know if there any other open points that could be interesting for the community or if there's anything else I should take into account.

Note: For now this is a draft as I'm still working on the code and modifying it

[google-cla]

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[yuvaltassa]

Please coordinate with @v-r-a who has been working on this feature for a while