Navigation superstructure

closes #2324 (closed) closes #2325 (closed)

This is for the channel only. We need to add grid-area: content to our views throughout the site. I'll do that later in a cleanup MR

It's missing some icons in the navigation sidebar until I talk to Michael about that, but you can review the rest @omadrid

** Testing **

• layout should be responsive. Left column should be thinner on tablet resolutions and it should be replaced by a hamburger menu and sliding menu on mobile resolutions