Added view for editing GradingRecords.
This view shows a list of GradingRecords if the id param is not present in the GET data.
Also renamed grading_record to view_records and fixed the redirect for that page
to also point to the GradingRecord edit page.
Made the locked property non-required.
This makes it easier to generate a Form that can properly deal with GradingRecords. Since required boolean properties can only be set to true by such an automatically generated form.