Under android/ directory, ignore:
GeneratedPluginRegistrant.java

Under ios/ directory, ignore:
GeneratedPluginRegistrant.h
GeneratedPluginRegistrant.m
Pods/

* Roll android build tools to 25.0.3

* Roll android build tools to 25.0.3 in templates

This reverts commit 5ed2984e.

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`.

* Add start-up test for flutter_view sample

* add reportMetrics flag to startup test

* rewording in manifest.yaml

* update Android part of flutter_view to use the new platform message channel.

* addressed comments

* addressed comments

* Add flutter_view sample

* Removed platform_services files

* Addressed comments

* update README.md

* Addressed comments.