Update docs

[AstraLuma]

Overview

Update the docs for some of the changes:

• Not sure when COUCHDB_CREATE_DATABASE disappeared, but I can't find anything using it
• Pretty sure ERL_COOKIE is a clouseau thing
• COUCHDB_USER/COUCHDB_PASSWORD have been required since the copsgood sense broke up the admin party

Testing recommendations

Run the YAML

Checklist

• Documentation reflects the changes;

[janl]

why the file rename? the target directory for this is $prefix/etc/local.d/ where a generic config doesn’t say much.

[AstraLuma]

Mostly because it contains both nouveau and non-nouveau config