Problem: configuration docs are not generated automatically

[sevein]

artefactual/archivematica#845 added a document (or documents, one per component) where the environment variables are listed. This work was done manually but it should be possible to update appconfig.py so it can output the full list as long as the details are included in the CONFIG_MAPPING. We could add a new method that outputs the list so it's later added to the Markdown file or we could even have the method to update the Markdown file dynamically and then commit it.

Other ideas that could be easily addressed once it's automated:

• Also include lookup path in the INI files that we support.
• Support config aliases (something that it's been added to AM18 or dev/1.8.x branch)
• Better ordering (alphabetic? by section + alphabetic?)
• Document the possibility of not having to include the section name in the env var, e.g. ARCHIVEMATICA_MCPCLIENT_MCPCLIENT_FOOBAR and ARCHIVEMATICA_MCPCLIENT_FOOBAR both should work.

[scollazo]

We can also consider moving them to the root package folder (MCPServer/README.md instead of install/README.md )