Force certain email domains to use SSO (DEV-579)

With this update, upon request, certain email domains can be blocked from using the Virbela username and password input fields, forcing those users to use SSO to log in. Users will see an error message if they attempt to log in with a restricted domain.

Minor In-World UI Changes

The bold style for agreeing to legal terms has been removed from the registration page (DEV-569)

Gradient has been removed from the title bar on the registration page (DEV-569)

Minor changes in the icons for the Userlist and GO TO menu (DEV-582)