Added user-interface for "Everyone Else" entity permission item

Nothing on back-end logic done to hook this new option up.
Addition of permissions for role_id=0 works out of the box, but active
"everyone else" permissions, with no priviliges, is currently not
working. Needs change of permission gen logic also.

app/Auth/Role.php

@@ -120,6 +120,19 @@ class Role extends Model implements Loggable
             ->get();
     }
 
+    /**
+     * Get a role to represent the case of 'Everyone else' in the system.
+     * Used within the interface since the default-fallback for permissions uses role_id=0.
+     */
+    public static function getEveryoneElseRole(): self
+    {
+        return (new static())->forceFill([
+            'id' => 0,
+            'display_name' => 'Everyone Else',
+            'description'  => 'Set permissions for all roles not specifically overridden.'
+        ]);
+    }
+
     /**
      * {@inheritdoc}
      */