Added ability to restrict OAuth logins by domain name (and bugfixes)

[eschwim]

• Added ability to restrict OAuth logins by domain name.
• User display names now get populated.
• Fixed a bug where multiple admin email addresses would fail to match all but the last match (looks like there was some mystery whitespace left over and the end of the strings after the explode).
• Removed the 'groups_provisioning' permission from the google auth request, as it doesn't appear to be used and forces the user to click through an additional screen.