This change adds a syntax for bootstrapping Angular on a page that allows more fine-grained control of the hierarchy created. platform() creates a platform injector (of which there can only be one). From the platform, .application() creates an Angular application including a Zone and all specified application bindings (e.g. for the DOM, HTTP, Compiler, Renderer, etc). At the application level, .bootstrap() will bootstrap the given component into that application.
Closes#3852