change of license

[orbeckst]

• As of 2024-06-21, NumFOCUS holds all rights on the MDAnalysis logos and any future logos that the project creates for itself.
• Removed the CC-BY-ND license from the MDAnalysis Atom logo.
• Made clear that all logos (Atom, MDAKit Registry) now can only be used outside MDA when following https://numfocus.org/trademark-guidelines
• updated READMEs with links
• close #6

[orbeckst]

Thanks @jennaswa !