Bring Typescript branch up to date

This is a very rough first cut at bringing the Typescript branch up to date with upstream generator-angular.

It doesn't work: a definition for "typescript" is missing at template time, probably due to a naïve merge of app/index.js, particularly with respect to Generator.prototype overrides. Add to that that I'm a JavaScript neophyte, to say nothing of Yeoman, Grunt, and Bower, and you have a recipe for disaster. :-)

However, I want to learn Typescript and AngularJS, so this seems like the best approach: trying to contribute. So sorry it's broken right now, but I'm hoping, with a little help, we can get it across the finish line.

Thanks!