Move user documentation links from imagej.net/BoneJ to https://imagej.net/plugins/bonej

[mdoube]

Describe the bug ImageJ Wiki docs have been / are being moved from imagej.net to https://imagej.github.io/

Links need to be updated.

• [ ] bonej.org index.html
• [ ] bonej.org legacy.html
• [ ] README.md #297
• [x] elsewhere such as the 'Help' buttons in some plugins' dialogs.

Additional context https://forum.image.sc/t/imagej-wiki-is-read-only/39672

the BoneJ page just got moved to https://imagej.net/plugins/bonej from https://imagej.github.io/BoneJ