Move mojo and mojom from mojo/public/dart to mojo/dart/packages

mojo/public/dart/mojom/bin/mojom.dart

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'dart:io';
-
-import 'package:mojom/src/command_runner.dart';
-import 'package:mojom/src/utils.dart'
-    show CommandLineError, GenerationError, FetchError;
-
-main(List<String> arguments) async {
-  var commandRunner = new MojomCommandRunner();
-  try {
-    return await commandRunner.run(arguments);
-  } on CommandLineError catch (e) {
-    stderr.writeln("$e\n${commandRunner.usage}");
-  } on GenerationError catch (e) {
-    stderr.writeln("$e\n${commandRunner.usage}");
-  } on FetchError catch (e) {
-    stderr.writeln("$e\n${commandRunner.usage}");
-  }
-}