Restructure around `products`

We've introduced the concept of products to third-party-web that can be subsets of an entity's resources.

Guidelines:

• An entity is a thing with distinct independence that offers some web functionality. It isn't necessarily a company, but at least a large group. Create an entity when that group has clear ownership over some set of domains, a distinct logo/brand identity, or obvious distinction from their parent company. Examples: Google Maps, ZenDesk, Instagram
• A product is some subset of functionality offered by an entity. Create a product when an entity does multiple different things that need to be further segmented. Examples: Google Maps Embedded API, Zendesk Zopim, Instagram Ads (for conversion tracking)

We want to add this guidance to our README and restructure a few of the entities that make more sense as products (mostly the major players that are thrown together, a few popular libraries, etc)

Start with the README and the current entity definitions. Apply the entity-versus-product guidance, then restructure the major players and popular libraries identified by the repository's data. Done means the README documents the distinction and the affected entries consistently use products where appropriate.