Icon Font Update

Updated icon fonts to include. Docs to be updated after this PR is merged.
- Hamburger
- Plus
- Minus
- Grid view
- List view

Also moved the inline collection view JS into `shop.js`.

This lets us delete the inline svg icons previously used for collection views, while adding a few more commonly used icons to the set.

Edit: also moved collections and blog sidebars below main content with `grid--rev` on mobile sizes. Should be its own PR, but minor enough I tacked it on here.

@mpiotrowicz @stevebosworth 
there's no copy in this fallback text, is it needed? Fallback should be there if an icon isn't accompanied by any visible text or if the text isn't representative of what the icon shows. eg. if the icon wasn't there, would something still be actionable and would users know what it did? cc @stevebosworth