Contributes to #2407
- Dropped the “2” in “Angular 2” and “angular2_*” where appropriate.
- Did a partial sync of `_cache/guide/pipes.jade`
- In quickstart, changed `Try changing the message to "Hello Angular
2!”` to `Try changing the message to "Hello Again Angular!”`.
* update to beta.22
* Dart SDK 1.19.0 or later is required
* minor edits to sample app titles to e2e tests pass
* Renamed “Angular 2” to “Angular” so that shared e2e tests pass.
* Tweak to QS prose.
