Move configuration out of setup.sh

Created a new file, setup.conf.txt, which should be copied to setup.conf and edited. Eventually, setup.sh.txt and regen.sh.txt can be moved to the final file names – however, that isn't a simple deployment issue, since developers currently have customized files at those locations.

I think it would be better to deprecate these files in favor of PHP scripts in the long run, because we will benefit from being able to search for and parse civicrm.settings.php, and so on.