Revamp resources listing, part 1 (frameworks/base)

- Revamp resource index page with big icons for resource types and a category listing.
- Update resource TOC to show resource types and topics, instead of actual resource links.
- Add resource browser/search results page (browser.html?tag=foo).
- Add resources-data.js file containing metadata and links to all resources.

Change-Id: Ieca87c6e42dda3c609824b71fb8a638abb11850c