Re-work Categories #71
Description
Instead of a page with links for each category (like tags), promote the category content to front-page-like status:
- Refactor the home-page template to be a general "headlines" page
- Move general, headlines-oriented functionality into discrete functions
- Convert home-page generating function to a category page of type "front-page"
- For each category, have a category page of the given category's type
- Update category links on the sites to point to these new headline pages for each category
- Support good user experience for new category pages:
- Update the category page to use full-width page
- Add a left column that lists all categories in the system as stacked pills nav menu
- Make right column the main content area that's like the home page / headlines (but for just the selected category)