[Soc2014] Official meta API

hi @carljm thanks for the comment.
As a matter of fact, it is! For legacy reasons, only GFKs are automatically excluded from get_field()'s search map.
In fact, for this reason, at Duth I had a chat with @akaariai that confirmed to me that it was just a legacy thing and that get_field() must be able to also return GFKs.

Have a look at this test case:
https://github.com/django/django/blob/master/tests/model_meta/test.py#L654

As we are refactoring the entire API, it makes sense to allow GFKs now