Site registry requirement errors displayed one at a time

The errors for required site information needed for site registry display one at a time. This means that the first time I go to set that up I am told I need to set my slogan. I go do that and then return to site registry. Now I'm told that I need to set my mission statement and I go back to settings again, etc. All errors should be reported at the same time so I can fix them all at once. This meant changing the form_set_error field name to different names so they can all display simultaneously. Note that the existing field name (drupal_directory) isn't a real field anyway.

Since site name is required and comes with a default, it only needs to print an error regarding site name being set to Drupal. I also removed the email error since it is required on the site information page and at install.