Clean up "grid" style pages

Pages like https://association.drupal.org/membership/benefits and https://association.drupal.org/projects should be horizontally aligned to the site's grid, and not vertically centered.

In the Views admin, those page displays should be in the "HTML list" or "Unformatted list" format. (The grid puts the elements into a table which we can't make responsive in the future.)

Then in bluecheese's CSS, use Susy mix-ins, http://susydocs.oddbird.net/en/latest/susyone/#basic-mixins, to get the container markup into columns.