update blue hex values

to match https://github.com/alphagov/govuk_frontend_toolkit/pull/80
Update toolkit to latest version

Gets this lot:
https://github.com/alphagov/govuk_frontend_toolkit/compare/ccbc4057...1c4f5a26

Highlights: new blue, some more images, more javascript.
Merge pull request #297 from alphagov/blues-become-one

update blue hex values