framework: Add dbus method set_filter()
    
    org.fedoraproject.SetroubleshootdIface.set_filter(ss) -> b
    
        Sets a filter on an alert. The alert can be "always" filtered, "never"
        filtered or "after_first" filtered.
    
          arguments
    
            local_id(s): an alert id
            filter_type(s): "always", "never", "after_first"
    
          return values
    
            success(b)
    
    Fixes: https://github.com/fedora-selinux/setroubleshoot/issues/24