Add generated API docs

[bwrrp]

I've experimented with typedoc earlier to generate docs, but there are still a few issues:

• Find a way to omit internal fields and types from the docs (some of these are public because they need to be accessed from other types, but internal to the library)
• Wait for a typedoc release for TypeScript 2.3.4
• TypeError: Cannot read property 'forEach' of undefined TypeStrong/typedoc#513
• Set up a gh-pages site and put docs there

[bwrrp]

@private may work to hide the internal properties and types.

[bwrrp]

I've moved over to Microsoft api-extractor / api-documenter, which seems to work well. TODO's at the top still apply.