As part of https://github.com/alphagov/notifications-admin/pull/187 the file
upload pattern was changed to auto-submit once a file had been picked. The
form that was submitted was, however, missing a CSRF token, as well as a submit
button for non-JS users.
This commit makes the file upload pattern self-contained, so that it will always
include a form with a CSRF token in a hidden input and a submit button, which is
then hidden when Javascript loads.
The ‘manage templates’ page was almost identical to the ‘send text messages’
page.
This commit consolidates them into one and makes them all hang together.
Part of this means tweaks to the javascript so that files upload as soon as
you’ve chosen them.