Organize client operations, split into modules, order by CRUD

[timvisee]

This does a (hopefully final) run on improving navigability in the client operations.

Most importantly:

• it splits operations into modules, similar to what we have in our main documentation
• it orders operations to follow CRUD - create first, delete last
• improves navigation by linking to the different sections

This only has cosmetic changes. No code/logic changes.

For example:

All Submissions:

• [x] Contributions should target the dev branch. Did you create your branch from dev?
• [x] Have you followed the guidelines in our Contributing document?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. [x] Does your submission pass tests?
2. [x] Have you formatted your code locally using cargo +nightly fmt --all command prior to submission?
3. [x] Have you checked your code using cargo clippy --all --all-features command?