Add new footer design.

Only show footer for transaction dashboards.
Add styles for new footer design.

Amend related_pages styles so they work in both the header and footer.
Update Stagecraft stubs for new footer design
Update cucumber tests.

Remove explicit classes from sections in the footer, since we don't
need them.

Add generic cucumber test for footer sections.

Update cucumber tests for .related-pages to deal with the fact that
this now exists in both the header and the footer.
Add missing apostrophe in description
Indent correctly
Use standard grey
Merge pull request #298 from alphagov/feature/new-footer-design

New footer design for dashboards