Documentation repo and build

[hdeshev]

Use the {N} docs. Introduce a conditional build that hides/shows Angular2 content.

[NathanWalker]

This sounds nice. Lemme know if I can assist in anyway here. 👍

[hdeshev]

Pushed the changes to the docs repo (master branch), and documented them a bit.

I also went over most of the content and hid topics that don't make sense in the Angular context (bindings, dependency properties, etc). Conditionally switched a lot of code for the nativescript build env and added TODO sections for its Angular equivalent. Still a lot of work left to be done there.

Oh, and we now have a "Cookbook" section enabled only for the angular environment.