COM AND COM VELOCITY multinode constraints

[Ipuch]

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• Have you followed the guidelines in our Contributing document [docs/contribution.md]?
• Have you checked to ensure there aren't other open [Pull Requests] for the same update/change?
• Have you opened/linked the issue related to your pull request?
• Have you used the tag [WIP] for on-going changes, and removed it when the pull request was ready?
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New Feature Submissions:

1. Does your submission pass the tests (if not please explain why this is intended)?
2. Did you write a proper documentation (docstrings and ReadMe)
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Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new examples for your core changes, as applicable?
• Have you written new tests for your core changes, as applicable?

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This change is 

[pariterre]

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Ipuch)