Moved most of html lib generating scripts into tools.

tools/dom/templates/html/dartium/impl_MouseEvent.darttemplate

 // Copyright (c) 2012, the Dart 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 file.
 
 // WARNING: Do not edit - generated code.
 
 part of html;
 
 /// @domName $DOMNAME
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   factory $CLASSNAME(String type, Window view, int detail, int screenX,
       int screenY, int clientX, int clientY, int button, [bool canBubble = true,
       bool cancelable = true, bool ctrlKey = false, bool altKey = false,
       bool shiftKey = false, bool metaKey = false,
       EventTarget relatedTarget = null]) =>
       _$(CLASSNAME)FactoryProvider.create$CLASSNAME(
           type, view, detail, screenX, screenY,
           clientX, clientY, button, canBubble, cancelable,
           ctrlKey, altKey, shiftKey, metaKey,
           relatedTarget);
 $!MEMBERS
 }