Core config wizard needs TLC

[dgw]

While repeatedly setting up new bots to test new (or repackaged) plugins with sopel-config init, I began to notice little things that don't make sense any more.

The core section's configure() wizard is pretty simple, and there are quite a few more basic options that it doesn't help set up:

• Authentication
• Admins other than the owner
• Account names for owner/admin
• Plugins (just whether builtins should be enabled on this config or not; managing beyond this is for sopel-plugins to do)
• The command prefix
• Logging
• The bot's user and ("real") name

On top of that, the main thing that got me thinking about this was outdated messaging in the prompts, e.g. "separated by commas" when prompting for the list of channels to join when ListAttribute now expects values to be entered on separate lines.

Overall, giving the config wizard some attention would be a nice QoL improvement we could do in a minor release (tentatively, 8.1).