* docs(quickstart): post-RC5 Dart resync
- Resync Dart QS prose with TS, post RC5.
- Added to-be-shared Jade `var` definitions to `_util-fns.jade`.
- Delete cached QS jade file.
- Eliminate the stub file `styles.1.css` in favor of a `docregion` in
the main `styles.css`.
This commit requires a `gulp add-example-boilerplate` after pulling it in.
Contributes to #2077.
* post-review edits
