Add a transformer for `di` which generates `.ng_deps.dart` files for all
`.dart` files it is run on. These `.ng_deps.dart` files register
metadata for any `@Injectable` classes.
Fix unit tests for changes introduced by the di transformer.
When using `pub (build|serve) --mode=ngstatic`, we will also generate
getters and setters, parse templates, and remove import of `dart:mirrors`
in the Angular transform. Because this is still relatively immature, we
use the mode to keep it opt-in for now.
Closes#700
Tim Blasi