Require Opt-in for use of local users (Windows Active Directory User Source)

If this user source is enabled without any configuration, it allows users to sign-in as local Windows users. (Unknown if this is also true for Linux.) While this is "expected behavior", it was unknown to me. ScreenConnect should change this behavior to opt-in.

• A checkbox, unticked by default, which allows an administrator to enable local user authentication. (If neither Active Directory nor the box is ticked, the user source should not be allowed to stay enabled in an unconfigured state.)
• This functionality is moved to a separate user source.