* Fix xcode_backend.sh script to support add2app

* Fix ios deployment target. Too old for new Xcode.

* Fix ios host app

* Register plugins with Flutter view

* Prototype

* Fix paths to Flutter library resources

* Invoke pod install as necessary for materialized modules

* Add devicelab test for module use on iOS

* Remove debug output

* Rebase, reame materialize editable

* Add devicelab test editable iOS host app

* Removed add2app test section

See https://github.com/flutter/flutter/pull/10000

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.