feat(platform): run in node-webkit and the browser

- Clean up IAppPlatform and expose it as an explicit interface.
- Move platform objects into source/platform, and compile them as a separate typescript task called 'platforms'
- Rename platform service to $platform so that it matches expectation of angular service by convention.
- Add grunt develop:web that will start a connect server for running in the web.

TODO: Enumerate files for BrowserPlatform, and Heroku deploy for web app.
refactor(platform): file tree in browser