* Update examples to lower the deployment target on iOS.

* Remove stray PRODUCT_BUNDLE_IDENTIFIER

This was erroneously added and overrides
the bundle for the gallery causing signing
to fail in my setup.

@chinmaygarde

* Remove PRODUCT_BUNDLE_IDENTIFIER from all Runner pbxproj's

Previously it wasn't included in the Runner target.

This patch changes the default `flutter create` command to generate a
HelloServices-style app on iOS. As a consequence, the Atom integration now
fully works with HelloServices.