* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

The following changes are made by this PR:

 * Translation bundles now implement MaterialLocalizations directly,
   and are public so that they can be directly extended.

 * The list of supported languages is now a generated constant.

 * The icuShortTimePattern/TimeOfDayFormat values are now pre-parsed.

 * Various other changes for consistency with the style guide and the
   rest of the codebase, e.g. the class names don't use `_`, the
   `path` library is imported as such, more dartdocs, fewer `//
   ignore`s, validation using exceptions.

This reduces our technical debt benchmark.

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

This is not a grand refactor yet, it's just cleaning up what we have
already, so that people who keep using this API (e.g. dialogs) have
something coherent to deal with.

The major changes are that Navigator and NavigatorState have the same
API now, that most of the examples use `<void>` instead of `<Null>`,
that the navigator observer can see replaces, and that the `settings`
is moved from ModalRoute to Route. I also cleaned up some of the API
documentation.

* Fix inherited widget notifications in Localizations

* address comments

* Make an app's supported locales configurable

* Added an supportedLocales.isNotEmpty assert

* WidgetsApp no longer const because supportedLocales.isNotEmpty

* updated per review feedback

* tweaked dartdoc to restart the build

* updated per review feedback

* Updated per review feedback