Lukas Riedel authored Feb 26, 2020 and Santiago Ospina De Los Ríos committed Feb 26, 2020

* Moved `COPYING.md`, `CODE_OF_CONDUCT.md`, `CONTRIBUTING.md`, and `LICENSE` (download only) into user manual #177.
* Fixed formatting of GMSH command #177.
* Fixed various links in existing documentation.
* Updated link to user manual in CLI.
* Added hints on cook book to `README.md` and user manual index.
* Fix render of `README.md` tables in user manual.