[Migrations] Keep track of a Edition's start/end time.
[Views] Moved the submission form views to a more appropriate directory and added a view for when submissions are closed.
[Models] Made 'submit' a reserved Submission slug, since we'll be using that in a route.
[Models] Handle timestamps for Social Profiles.
Added a route for the submission form.
[Controllers] Display a note when submissions are closed and disallow POST to controllers\Entries::store() when out of a Edition's running timeframe.