Rationalize Dart mojo and sky package structure

sky/framework/elements/sky-menu-divider.sky

Index: sky/framework/elements/sky-menu-divider.sky
diff --git a/sky/framework/elements/sky-menu-divider.sky b/sky/framework/elements/sky-menu-divider.sky
deleted file mode 100644
index d83f70ab00f4ac65625c051eeae48d3cfa3d9686..0000000000000000000000000000000000000000
--- a/sky/framework/elements/sky-menu-divider.sky
+++ /dev/null
@@ -1,26 +0,0 @@
-<!--
-// 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 src="sky-element.sky" />
-
-<sky-element>
-<template>
-  <style>
-    :host {
-      margin: 8px 0;
-      border-bottom: 1px solid rgba(0, 0, 0, 0.12);
-    }
-  </style>
-</template>
-<script>
-import "dart:sky";
-
-@Tagname('sky-menu-divider')
-class SkyMenuDivider extends SkyElement {
-}
-
-_init(script) => register(script, SkyMenuDivider);
-</script>
-</sky-element>