- Add TOC
- Better describe what RFsim does
- Remove misleading, wrong, unnecessary information
  * It is futile to mention --phy-test or other modes, RFsim works with
    all
  * Explaining how to ping is not the task of the RFsim documentation
    (that is what tutorials are for)
  * Remove useless/outdated build log information
- Add some more information on which flags to run
- Improve formatting, and minor clarifications