Object handler fields override local field list
When defining a handler for one object that relates to another, any field that references an object with a handler defined are overridden by the referenced object's handler.
class HandlerFoo(BaseHandler): model = Foo ....
class HandlerBar(BaseHandler): model = Bar fields = ('blah', ('foo', 'zing', 'zang')) ... }}}
Assuing 'foo' is a foreign key referencing a 'Foo' object, When the response for HandlerBar is rendered, all the fields on Foo are rendered, even though I specifed only the 'zing' and 'zang' fields.
Local field specs should always have precedence over the field spec on other handlers.
The attached patch changes the precedence.