Strange __view__ behaviour

[filmackay]

When specifying a __view__ - I'm not expecting form_columns to be set to column_list. Any objections to a PR for model/utils.py:146 to instead:

                assert issubclass(cls.__view__, ModelView)
                admin_view_class = cls.__view__

Similarly for the show_pks case - why reset form_columns?

Out of interest, how can I replicate the default behaviour (no form_columns provided) with some actual form_columns values? Give it fields, and relationships - but no foreign key columns?