Rename the _fletch_system and service and dart: libraries

samples/todomvc/dart/todomvc_service.dart

 // Copyright (c) 2015, the Fletch project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 // Generated file. Do not edit.
 
 library todomvc_service;
 
 import "dart:fletch";
 import "dart:fletch.ffi";
-import "dart:service" as service;
+import "dart:fletch.service" as service;
 import "struct.dart";
 
 final Channel _channel = new Channel();
 final Port _port = new Port(_channel);
 final ForeignFunction _postResult = ForeignLibrary.main.lookup("PostResultToService");
 
 bool _terminated = false;
 TodoMVCService _impl;
 
 abstract class TodoMVCService {
@@ skipping 197 matching lines @@
   void operator[]=(int index, int value) { segment.memory.setUint8(offset + index * 1, value); }
 }
 
 class _PatchList extends ListReader<Patch> implements List<Patch> {
   Patch operator[](int index) => readListElement(new Patch(), index, 32);
 }
 
 class _PatchBuilderList extends ListBuilder<PatchBuilder> implements List<PatchBuilder> {
   PatchBuilder operator[](int index) => readListElement(new PatchBuilder(), index, 32);
 }