Moving back to go.dedis.ch/dela

[ineiti]

This PR moves all the imports and module name back to go.dedis.ch/dela. Then a 'replace' directive in the go.mod will point to our fork.

Thank you for opening a pull request with this project, please also:

• add a brief description of your changes here
• start in draft mode and in progress pipeline in the project (if applicable)
• once it's ready put it in the Review or Ready4Merge pipeline in the project (if applicable) and remove draft
• assign a reviewer
• if applicable, add this PR to its related issue by one of the special keywords (https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/using-keywords-in-issues-and-pull-requests#linking-a-pull-request-to-an-issue)

[ineiti]

Will make a 2-commit PR in #59