Adding typescript support to generator-angular

There have been a few other projects that have tried to support typescript with the angular generator (e.g. [anchann](https://github.com/anchann/generator-angular) and [JakubMrozek](https://github.com/JakubMrozek/generator-angular-typescript)), but are currently out of date. It would be great if we could get this merged in so that we can try keeping it current.