New curricula design exploration

Working through some design revisions to add other curricula to OCP site. Here's the list of style guide changes:

* Add other curricula to Our Curriculum index page
* Add other curricula to homepage grade selector
* Add a "switcher" component to switch between available curricula in the homepage grade selector
* Add styles and js for the switcher
* Change style of titles in curriculum-list elements so titles appear more like standard links
* Do the same for search results
* Incorporate curriculum abbreviation (e.g., "ELA") into Grade landing page title and component IDs to see how it works
* Adjust curriculum component IDs on lesson page to reflect current practice
* Add "ELA" to breadcrumb for the sake of comparison