Allow for nicer URLs when linking to pages

We can now link using ?organisation=... etc, instead of using a gigantic
Rails nested form.
Unify filter pages, add classes
Style
Make feed/email icons display-block

Use the magic cross browser version from govuk_frontend_toolkit
Copy across filter params to email link
Dynamically update email link via Ajax
Don't respect 'all' parameters
First few tests
Tests for application helper