Implement flutter format, fixes https://github.com/flutter/flutter/issues/5338

* implement flutter packages get/upgrade command
* alias flutter pub
* refactor findProjectRoot for use by multiple commands

fixes https://github.com/flutter/flutter/issues/4994

* add flutter channel command
fixes https://github.com/flutter/flutter/issues/2513

* fix test

* address comments

* remove unused imports

* fix lints

- [x] Update engine to bring in new snapshotter.
- [x] Use the new snapshotter to quickly determine the minimal set of files necessary to run.
- [x] On first DevFS sync, only sync files necessary to run the application.
- [x] Fix a DevFS unit test failure.
- [x] Include DevFS tests in all.dart.

* make flutter run work with a pre-built apk

* refactor to remove the buildDir param

* making flutter run work with gradle

* locate android studio

* add test for settings

* review comments

This prevents multiple simultaneous runs of the analyzer from stomping
over each other (e.g. multiple runs of 'update-packages'). Certain
long-lived commands (like analyze, run, logs) are exempted once they've
done enough work to be safe from most stomping action.

This still doesn't make us entirely safe from craziness, e.g. if you're
half way through an 'update-packages' run and you call 'git pull', who
knows what state you'll end up in. But there's only so much one can do.

Fixes https://github.com/flutter/flutter/issues/2762

* rename service_protocol.dart to protocol_discovery.dart

* add a wrapper around the obs. protocol

* use json-rpc in run

* consolidate obs. code; implement flutter run --benchmark

* review comments

* add google analytics

* send in the run target type

* track device type targets

* use the real GA code

* review comments

* rev to usage 2.0

* rev to 2.2.0 of usage; add tests

* review comments

* use the new cache code to locate more artifacts

* add todo

* review comments

* more terse flutter upgrade

* fix an issue when updating and the engine update code has changed

* call flutter precache; add a --no-color hidden option

* fix a lint related to getters/setters

wrap up first daemon implementation