Followup to #427

Also improved the CHANGELOG

A better example of proper usage, too – IMHO

Closes https://github.com/google/stagehand/issues/425

* Remove platform* options.

* Update CHANGELOG.

Also:

* update to angular_components 0.5.1
* Ensure tool/grind.dart build ignores build directories

Fixes #396

Forgot to merge Patrice's PR before pushing. Oops.

* [WIP] Add angular_test based tests to web-angular-simple

Fixes #386

* Update to angular2 3.0.0-beta+1
* update ACX and NG vers in web-angular-*
* update SDK to 1.23.0 for web-angular-*
* validate_templates: allow SDK 1.23.0 for angular templates
* Update pubspec and changelog version to 1.1.1-dev, 1.1.1

- Standardized the layout of `pubspec.yaml` for all templates.
  - Consistent ordering of all top-level keys
  - Use `^` notation for versions.
  - Define the minimum SDK to be `1.20.1`.
- Simplified `.gitginore` for all templates.
  - No longer need to ignore `packages` directory. They are not not generated
    with SDK 1.20.1+.
  - No longer ignoring compiled outputs by extension. These will all be in the
    `build` directory, which is already ignored.
  - No longer ignoring JetBrains IDE files. These should be ignored in a users
    global `.gitignore`.

Also added tests to validate many of these things

Fixes https://github.com/google/stagehand/issues/372

* update web templates

* add web-angular-quickstart
* remove web-polymer
* update web-angular

* Update CHANGELING and version

* make tests pass

* tweak web-angular description

* Fix copyright year.