Add GOV.UK look and feel

Add sign-out link
Split Admin interface into two namespaces

One for notes and one for synonyms, because even though the layout is
similar they are meant to change different things
Merge branch 'govuk-styling' into 58867026-govuk-styling

Conflicts:
	app/views/layouts/application.html.erb
Fix link to Trade Tariff Admin
Fix fluid content style
Replace nav_link helper with regexp-based one
Remove now redundant controllers and views
Merge branch '58810098-admin-pages-redesign' into 58867026-govuk-styling
One bootstrap gem is enough

Use the one Publisher uses
Add submit button disabling, remove redundant views
Merge pull request #11 from alphagov/58867026-govuk-styling

GOV.UK styling and Admin UI updates

https://www.pivotaltracker.com/story/show/58810098
https://www.pivotaltracker.com/story/show/58867026
https://www.pivotaltracker.com/story/show/58867014