Gradle projects are evaluated in lexicographical order, and the plugin
projects are at the same level as the :app project, so if a plugin has
a name that comes before 'app' (like, for example, any name that starts
with a capital letter), the plugin project will be evaluated before
:app.
Since :app applies the Flutter Gradle plugin, which tries to
modify the dependencies of the plugin projects, we have a problem if the
plugin projects have already been evaluated. Adding
evaluationDependsOn(':app') to the plugin projects fixes this.
Updated example projects to the latest (plugin-enabled) Gradle build
files.
Also removed two unused imports in `pluginClass.java.tmpl`.
* Update hello_world to new gradle based build flow
* Update flutter_gallery to gradle based build
* Align hello_services with new gradle based build
* Update platform_services to new gradle based build
* Upgrade stock to gradle based build
* s/sky/flutter/ in Android templates
* update engine.version with a compatible engine version
* replace more SkyActivity references with FlutterActivity
