Rationalize Dart mojo and sky package structure

sky/sdk/lib/framework/layout.dart

 library layout;
 
 import 'node.dart';
 import 'dart:sky' as sky;
 import 'dart:collection';
 
 // UTILS
 
 // Bridge to legacy CSS-like style specification
 // Eventually we'll replace this with something else
@@ skipping 477 matching lines @@
   print(prefix + node.toString() + _attributes(node));
   var children = node.getChildNodes();
   prefix = prefix + '  ';
   for (var child in children)
     _serialiseDOM(child, prefix);
 }
 
 void dumpState() {
   _serialiseDOM(sky.document);
 }