Made a start on scenarios for managings attachments

Note that we are putting these in a sub-folder. Will probably need to
update the cucmber config/jenkins scripts to cope with this.
Basic controller for attachments
Improve double-click protection behaviour

Whilst we want to disable clicked submit buttons to prevent double
form submission, we still want the input to be sent with the form
payload. To do this, we include a hidden input with the same name and
value as the button. This is necessary because browsers do not
include disabled inputs with the payload.
fixup scenario
Adding attachments using new workflow

This gets the basics working. The existing forms are still present in
the UI for the moment. We'll refactor those in a later commit so just
the attachment information is listed without the form fields. We are
also ignoring the handling of consultation responses for now, we'll
get them working with the new workflow in a later commit.
Comment out unnecessary tests + those to be replaced
Tidy up publication steps

Removed a redundant step and set a more generic instance variable for
the attachment
Admin::AttachmentsController can edit attachments
Move generic test to GenericEditionsControllerTest
Add attachments when editing editions
Delete attachments from editions
Fix startup.sh check for SHOW_PRODUCTION_IMAGES
List editions attachments when creating/editing

This separates out the the listing of attachments on edition pages
from the existing workflow, which is remaining in place for other
models, e.g. policy groups, supporting pages, etc.
Remove bulk uploads from attachment_fields partial

Only editions use bulk uploads, and this partial is no longer used
with editions. Therefore we can drop all this logic from the partial.
Scenario for new bulk upload workflow
Start of an AR-like object for bulk uploads

This object represents a collection of attachments that are to be
saved to a "thing" (for now, probably just editions). We use this in
the bulk upload process, allowing the user to supply attachment titles
before we save them on-mass. Work in progress.
BulkUpload::ZipFile#extract_files returns paths

We no longer need separate filenames
Fix typo in form partial
Kill off old attachment management code

This commit removes all the code relating to the old way of managing
attachments. We no longer need to include the concern in our
controllers and we can kill off some of the macros that tested the
nested attachment behaviour (we still need one of them for now as it
is used for supporting pages and corporate information pages). We also
kill off the code that was used to manipulate the params based on any
bulk uploaded zip files.

Functional testing of attachments will now happen in
Admin::GenericEditionsController::AttachmentsWorkflowTest. There are
a couple of test cases still to be added there.
Add unimplemented test for display of attachments

This test replaces some of the tests that we've just removed...