- Remove multiple single top-level (# H1) headings per file
- Use (# H2 and ###### H6) sub-headings for consistency
- Remove any trailing # in the headings
- This ensures proper table of contents rendering in MkDocs.
- Also removed RUN_NR_multiple_BWPs.md as it is moved to MAC usage
- Do not list L1sim as a way of running OAI: it is untested, and might
not work
- Reword the tutorial where necessary, remove outdated/wrong information
(e.g., we don't test this mode AFAIK)