7.0 search payment methods with company

Fix for issue #51 
The context should not be mutated directly in the session, it should be changed with `with self.session.change_context(...):`. It should not be modifier in the Mapper since the Mapper should only take data in and return data out, and not use a side effect on the state of the Importer. The Importer has the responsibility to change the context for example before calling the creation or update of the record.