Expand SDF description on link kinematic property

[iche033]

🎉 New feature

Related PR: gazebosim/gz-physics#618

Summary

Added more documentation on what kinematic only mode means for a link. Consulted bullet / dart / ode documentation (as pointed out in gazebosim/gz-physics#618 (comment)) and extract common properties from their descriptions.

I think not all physics engine support joints between dynamic and kinematic links so I left that out in our SDF description.

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[caguero]

Typo: velcoity

[iche033]

Typo: velcoity

fixed cfdd686