Improved drush os-domain- scripts #1550

* List checks that domain is configured.
* Added override options for htaccess, domains, and sites.php.inc files.  Since we don't have perms to create sites.php.inc or domains.list on acquia, now we can place them wherever we like.
* Checked the options above.  They *can* be specified in a drush alias.

Haven't had a chance to check the cloud api thing yet.
Merge pull request #2457 from openscholar/1550-drush_domains

Improved drush os-domain- scripts #1550