Icon-step images are in a folder

The icon-step images were moved into a folder[1]. Update the Sass to look
for them in that folder.

[1]: https://github.com/alphagov/govuk_frontend_toolkit/commit/e523d51536482f3f300b798883c348e9d41bf2da
Merge pull request #1774 from alphagov/icon-steps

Icon-step images are in a folder
Remove IPO from the services & info page whitelist

Due to some content issues, we're removing the link to the Services & 
Information Page from the homepage of the Intellectual Property Office
at the current time.
Merge pull request #1775 from alphagov/remove-ipo-from-services-info-whitelist

Remove IPO from the services & info page whitelist
Publish Organisations to the Publishing API

As part of the work of moving other Applications to rely on the Content
Store we need access to Organisations. This work sends the Organisation
to the Publishing API after save which kicks off a worker and queues it
up to send to the publishing API.

This commit adds the content_id to the Organisation table. This is
generated and used by the content store as a UUID. It generates this on
a before_validation callback. There's also a data_migration to populate
the content_id for all existing Orgs.

Work was based off the work in 63e4f7c. Ticket:
https://trello.com/c/MUqfVwLp/358-getting-orgs-from-whitehall-into-content-store
Reinstate keyword-filter identifier.

Removed in a previous cleanup the containing element for the keywords
field on all document filtering needs to have a filter specific
elementId.
See:
https://github.com/alphagov/whitehall/commit/4c682d099fa0f77f042d01bcd39c5dd9d44f317d#diff-08e4a107c3401662ebf39b86de38b01cL11
Merge pull request #1777 from alphagov/fix_document_filter_text_search

Reinstate keyword-filter identifier.
Publishing guidance changes

The new content publishing guidance manuals are now live. These changes
point to the new guidance on style and how to publish to GOV.UK.
Merge pull request #1773 from alphagov/publish-orgs-to-publishing-api

Publish Organisations to the Publishing API - Tested locally. Correctly publishes to Content Store.
Point directly to plain English section

Point directly to plain English section of the publishing guidance
Fix add_content_id_to_orgs migration

With the migration added in ba5a421 there was both a `null:false` and
index on the new `content_id` column. This prevented the migration from
running as when it came to add the index all the rows in the column were
blank strings.

This commit changes the existing migration to add the `content_id`
column without the null constraint and updates the data migration to
look for Orgs with nil `content_id` fields instead of empty strings.
Merge pull request #1779 from alphagov/publishing-guidance-changes

Publishing guidance changes
Merge pull request #1778 from alphagov/fix-content-id-migration

Fix add_content_id_to_orgs migration
Remove organisation_id from StatisticAnnouncement

https://github.com/alphagov/whitehall/pull/1751

the change above introduces a join table to store
M-M relations between statistics announcements and
organisations. hence this column is not required.