Example: $ mojo:launcher mojo:spinning_square

This adds media.dart which was omitted from flutter_services and fixes
incorrectly generated copyright headers to reflect the current year.

This adds a flutter_services package responsible for exposing the Dart
interfaces exported by the engine in a uniform fashion, regardless of
how and where the generated code for the interfaces are organized.

Now lib/ui depends on sky/engine rather than the reverse.

This change disentangles the build for the snapshotter from the main engine
build. Also, we now have all the Dart files for dart:ui in the same directory.

* Update to mojo ba13534f2b2af27a1d73e176f7406dbab25f8e14

* Fix build for updated mojo

* Fix android build. Undo some of the mojo roll.

* Fix iOS build.

Previously we failed to copy these files to the correct place.

* Update to mojo fd8d18dbf7a4f9ed8a607648cca6d2c595b1c580

* Update mojo_sdk

* Update to account for Mojo API changes

* Backport to older base

These files are generated to different paths now.

This patch moves the geometry classes.

* Update to mojo 7d579155cc597aa3befcbfad66eef54bda06b57c

* Update to new API

* Update to mojo 9a791294e429f9f2ca4f427796a284edb6f6768e

* Update to account for Mojo API changes

These were forcing our customers to obey these lints, but not all of our
customers like them. We might enable some of these in the future if they have
concrete benefits (e.g., faster generated code when compiling ahead-of-time).

The layout protocol in Mozart changed. Now we need to pipe a scene version
through the system to the compositor.

We currently whitelist some types that don't need parameters. Turning on
this lint causes too many lint errors in Atom.

This patch updates _embedder.yaml to enforce the same set of lints as
`flutter analyze`. We're still not enabling strong mode via this
mechanism, but we might consider that in a later patch.

Related to https://github.com/flutter/flutter/issues/2687

* Add some missing dependecies to sky_services
* Create a script that excludes unnecessary files when preparing the package for release

This reverts commit 7bfce5cb.
This reverts commit a550e7e3.

We no longer use a pub package to distribute these icons.

This reverts commit ccd1c5ce, reversing
changes made to d4f97e4f.

This was requested by @johnmccutchan because this change broke the
analyzer, which only uses SDK version 1.14.1, since that's what we pull
in. He said he'd try again on Monday.

This patch merges these functions into dart:ui, which is simpler.

Fixes #83

I moved it to https://github.com/mpcomplete/flutter_gcm for now.