Add tags to robot descriptions database

[stephane-caron]

This PR follows up the suggestion by @drfenixion in #130 by adding a tags field to the list of robot descriptions.

Tags are implemented as sets of strings (rather than enumerations like we do for formats) to allow for various future usages. The current use case for tags is about morphology (e.g. "quadruped", "humanoid", ...), but in the future it may be pertinent to other use cases to filter over other features (e.g. "tendon_driven", "can_jump", ...)

This PR tags quadruped robot descriptions and adds an example showing how to load them all in Pinocchio:

[coveralls]

Pull Request Test Coverage Report for Build 14196394399

Details

• 13 of 13 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 97.89%

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Totals
Change from base Build 14195396351:	0.3%
Covered Lines:	1067
Relevant Lines:	1090

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💛 - Coveralls

[stephane-caron]

Added a similar example with humanoid robot descriptions:

[drfenixion]

@stephane-caron Great work! It also nice to tag manipulators, grippers, bipeds if you know what packages contain is.

Btw, I am integrating Robot_descriptions to RobotCAD and currently made most of work. I want to make categories in UI based on your tags. I would be grateful if you could merge this quickly.

You can see how is displayed imported models.

[stephane-caron]

Your project looks great 🤩

I've added a tag to each description based on the readme. Feel free to open a PR if you find some tags are missing.

I will merge this PR now, and aim for a release of v1.16.0 of the project by the end of this week.

[drfenixion]

Thank you for fast tags feature creating.
You don't have to rush the release, I'm using the repository as source instead of pip anyway.