Remove html entities from the html-ified body
Remove attachment references from govspoken bodies

We haven't extended govspeak to do this, so we have to do it manually.
New data migration to fix summaries with attachments or entities
Merge pull request #165 from alphagov/better-body-summarisation

Better body summarisation
Explicitly provide bulk_upload_zip_file to attachment_fields

This fixes the form for those editions that allow attachments on sub-objects, as otherwise all the attachment_fields would think there was a bulk_upload_zip_file available, but the JS doesn't really work if there are multiple bulk uploads on the page.

This should resolve: https://www.pivotaltracker.com/story/show/42961671
Add summary to fixture data for statistical data set import
Let the summarise_body_parser cope with nil input

Given how this is used, it's likely that an edition with a nil body would fail validation anyway so it's ok, and we should let the upstream objects validate their input.