Build universal armv7+arm64 binary for iOS now that our tooling supports
it.

* flutter update-packages

* update plugin registrant for flutter_gallery

Adds `Scaffold#endDrawer` property to supply a second drawer to a Scaffold.

See https://github.com/flutter/flutter/pull/10259

This reverts commit 4bbf158b.

* Revert "Update reference to url_launcher plugin in Gallery pubspec (#9879)"

This reverts commit 96a04dea.

* Revert "Revert "Revert plugin use in gallery (#9838)" (#9877)"

This reverts commit ede72a80.

This reverts commit 4bbf158b.

* Revert "add Podfile (#9835)"

This reverts commit 74e65675.

* Revert "update ref to url_launcher plugin in Flutter Gallery (#9833)"

This reverts commit 30c49781.

* Revert "Use url_launcher plugin in Flutter Gallery (#9751)"

This reverts commit 02dfd6be.

Enable plugin infra for both iOS and Android post-#9791.

* Revert "Update Hello World to latest iOS project template (#8634)"

This reverts commit 6dc6ed4e.

* Revert "Update Gallery to latest iOS project template (#8637)"

This reverts commit 84c42aac.

* Revert "Update Stocks to latest iOS project template (#8640)"

This reverts commit 90774c18.

Already enabled on Android.

Gallery and stocks:
* Add 20x20 notification icons.
* Remove unused 76x76 (3x scale) icon.

Other examples: update JSON to Xcode 8.2.1 defaults

Fixes warnings for missing/unused icon assets in Xcode 8.2.x

Subclassing FlutterAppDelegate is not required for real-world apps, but
it's what 'flutter create' generates, and applies the default behaviours
that most real-world apps will want.

Almost all real-world apps will want a custom app delegate, and 'flutter
create' code-gens one by default. This brings the samples in line with
our templates and the most common use case.

As of Xcode 7, Apple recommends setting the bundle identifier in the
PRODUCT_BUNDLE_IDENTIFIER build variable and setting CFBundleIdentifier
to that variable in Info.plist.

As of Xcode 8, CLANG_WARN_INFINITE_RECURSION and CLANG_WARN_SUSPICIOUS_MOVE
are recommended settings.

I took the logo_square from:
https://github.com/flutter/identity-assets/tree/master/assets/logo_square
Opened it in preview, gave it a white background
and then dropped it in the icon tool to create
these updated icons.

We may want to use offwhite like we did for Android
but this is sufficient for my demo today.

@hansmuller

We want to use the FlutterViewController in this new project template.

Fixes #4840

We now use a different approach for ios projects where the developer controls
the Xcode project file. This patch removes the old ".generated" approach in
favor of the new approach.