ddadd3db49 mass standardized the
formatting, with some errors.
This commit fixes errors on `login.md`:
- revert wrong `Logging out` headline
- restore correct level for some headlines (relative to parent
headline level change)
- re-add `Usage` headlines, with better name
Also add `related commands` headline on `login` and `logout`.
Signed-off-by: Thomas Riccardi <thomas@deepomatic.com>
a0e3ec8790