Purge outdated documentation

<img src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" decoding="async" class="lazy" data-src="https://img.shields.io/badge/reflectometry%20Task%20373%20-%20complete%20-%20grey">

Description:

Remove any developer's documentation inconsistent with the current containerization. For instance, installing and running software on the host machine, or running commands instead of invoking make targets.

Files containing deprecated documentation

• redesign documentation/
• developer/README.txt
• developer/installation.rst
• developer/testing.rst
• developer/settings.rst
• implementation-deployment/
• usage_scenario_monitor.rst
• developer/walkthroughs/SSH_keys_management.rst

These files will either be removed or repurposed with the outdated documentation removed