[development] Patching settings.php

[Khalid B]

I like the -dist idea by Earl, and what Jeff is proposing.

The other day, I did an install on my head checkout, and got SQL
errors, because I already had a subdomain.example.com directory
and settings.php in it.

So, I erroneously assumed that the installer does not touch settings.php,
and wrote an article about it, which several people (including Jeff) corrected.

Only when I copied the default/settings.php to the subdomain.example.com
was I able to see the installer work properly.

Yes, we should make the installer create the multi-site directories. This
means settings.php and themes at a minimum. Now that we have sites/all
in there, a per site modules directory is not needed in most cases.