* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

* WIP

* Added tests and updated SafeArea implementation.

* Analyzer nits

* Review feedback

* Updated for SnackBar and PersistentFooterButton cases, added tests to check other potential spots.

* doc addition for SafeArea

* Typos

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

As a convenience, this adds a set of minimum padding to apply. The
greater of the minimum padding and the media padding is applied to each
edge.

A SafeArea-like widget that applies a SliverPadding instead of a
Padding.

This attempts to apply some of what we learnt from UX studies, namely
that people wonder how to add multiple children to widget that take
one child.

* SafeArea

* AnimatedSafeArea

* AppBar test

* Apply feedback