Stop using `alternative_title` field

The `alternative_title` field has been removed from use from the
publisher application as of alphagov/publisher#292.

With this change, we stop using the field in frontend (where it's
exposed to the user) so that it can later be removed from the Content
API.

Note: the majority of the files changed here are test fixtures that
contained this field
Merge pull request #694 from alphagov/stop-use-alternative-title-field-for-editions

Stop using `alternative_title` field
Don't add 'the' to `will_continue_on` text

www.agileplannerapp.com/boards/173808/cards/8718

.. for business support editions. instead, give editors
flexibility to add that word from mainstream Publisher.
This keeps it consistent with other formats.
Merge pull request #695 from alphagov/fix-the-the

Don't add 'the' to `will_continue_on` text