fixes https://github.com/flutter/flutter/issues/5788

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

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

This change adds a top-level getBuildDirectory func and funcs for
android, aot, asset, ios build products.

Developers may now add a "build-dir" mapping to their
~/.flutter_settings (JSON format) config file. Output directory is
relative to the main flutter application directory.

This change also changes the default build directory for iOS builds to a
subdirectory of the configured build directory, 'build/ios' by default.

has been fully processed before completing the returned future.
This helps prevent tests that rely on stdout from being flaky.

* don't resolve symlinks as part of which

* update method dartdoc

* General improvoments to the loader app:
   * Show a message after 8 seconds if no connection comes in.
   * Show a progress bar as files are being uploaded.
   * Hide the spinner just before launching the application.

* General improvements to the "flutter run" UI:
   * Add "?" key as a silent alias for "h".
   * Make the help text bold so it doesn't get mixed with the logs.
   * Make "R" do a cold restart when hot reload is enabled.

* Supporting features and bug fixes:
   * Add support for string service extensions.

* Other bug fixes:
   * Expose debugDumpRenderTree() outside debug mode.
   * Logger.supportsColor was missing a getter.
   * Mention in the usage docs that --hot requires --resident.
   * Trivial style fixes.

* making flutter run work with gradle

* locate android studio

* add test for settings

* review comments

We now download the base coverage file automatically.

* Fix `flutter upgrade`

* Fix builds on iOS

Also, make it clear the screen between results so it's more obvious
what's going on when you have new results (especially when you have
fixed everything).

* refactor the --resident run option into a separate file

* update daemon to run --resident apps

* re-plumbing daemon start

* send app logs

* update tests

* review changes

* fix test runner

* remove PackageMap.createGlobalInstance; rely on the ctor

* review comments

* show build progress; print app sizes

* add todo

* review comments

* remove unused import

* working on making a faster flutter run restart

* clean up todos; fire events on isolate changes

* use the Flutter.FrameworkInitialization event

* review comments

This reverts commit 8f69cccc.

* dissallow -release mode on emulators

* have the help text print the default mode

This passes the information through Xcode to the `flutter build aot` call via
the environment so that it picks up the right artifacts.

Fixes #4186

* handle an exit code from android n

* review comments

* 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

* use vendored dart sdk; check the expected version of flutter

* search up directories looking for the flutter root

* send ext.flutter.exit

* listen for help restart, quit

* refactor into a separate class

* avoid sending analytics on ci systems

* review comments

* fix analysis errors

* review comments; fix test

* re-add an export for debugPrint

* rework flutter run

* fix npe with --debug-port

* connect to obs and exit when that conneciton closes

* update todos

* add a service extension for repaint rainbow

* review comments

Handy for testing against specific local SDK builds.

(Note that the option is hidden.)

* download android-arm-deploy

* wire up --deploy to android-arm-deploy

* fix interpolation