Generated.xcconfig is only required at build time for iOS apps. In the
flutter create project template and example apps, Generated.xcconfig was
previously marked as a resource to be bundled into the built app.

Updates all example projects to build as universal binaries that run on
both armv7 and arm64 now that we support both platforms on iOS.

This consolidates all of the non-template .gitignore rules into the top level .gitignore, to ignore common things more broadly, with less maintenance needed for the .gitignore files. Does not touch the templates, so that they still produce needed .gitignores as part of flutter create.

Under android/ directory, ignore:
GeneratedPluginRegistrant.java

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

* Add Pods cache dir to ios/.gitngnore

* Add missing ending newlines

See flutter/engine#3539

* Rename platform_services to platform_channel

* rename in README

* renamed tests

* update modules.xml