expand allowed types for tableRefFor and tableNameFor

it fixes:
Argument of type 'ModelClass<Foo>' is not assignable to parameter of type 'typeof Model'

typings/objection/index.d.ts

@@ -690,7 +690,7 @@ declare namespace Objection {
   }
 
   interface TableRefForMethod {
-    (modelClass: typeof Model): string;
+    (modelClass: ModelClass<Model> | typeof Model): string;
   }
 
   interface AliasForMethod<QB extends AnyQueryBuilder> {