This change is for https://www.pivotaltracker.com/story/show/58794800
Adds API endpoint for national footnote editing. Restricted with authentication.
Add Footnote API endpoint
Enable footnote description updating
Update footnote primary key order
It makes sense to compose it of footnote_type_id + footnote_id. Footnote
type id is indexed 2 char field and is shorter than footnote_id so it's
faster to query.
This does in place updates, updating existing national footnotes and keeping their validity periods unchanged. Two unsolved problems are: