Update 'CKAN Configuration Options' docs

I haven't used autodocs for this either because I couldn't think about a good place to put the file with all the documentations to be parsed. As, AFAIK, we can't use the docs inside the .ini files, it felt duplicated to try and create another file just to gather all config options and document them. That feels like the same as simply creating them directly into the .rst file.

Fixes #534