Move sky-box,-button,-checkbox,-radio out of their directories

examples/window_manager/debug_panel.sky

 #!mojo mojo:sky_viewer
 <!--
 // Copyright 2014 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.
 -->
 <sky>
 
 <import src="/gen/examples/window_manager/debug_panel_host.mojom.sky" as="example" />
 <import src="/mojo/services/navigation/public/interfaces/navigation.mojom.sky" as="navigation" />
 
 <import src="/sky/framework/embedder.sky" as="embedder" />
+<import src="/sky/framework/sky-box.sky" as="SkyBox" />
+<import src="/sky/framework/sky-button.sky" as="SkyButton" />
+<import src="/sky/framework/sky-checkbox.sky" as="SkyCheckbox" />
 <import src="/sky/framework/sky-element/sky-element.sky" as="SkyElement" />
-<import src="/sky/framework/sky-button/sky-button.sky" as="SkyButton" />
-<import src="/sky/framework/sky-box/sky-box.sky" as="SkyBox" />
-<import src="/sky/framework/sky-checkbox/sky-checkbox.sky" as="SkyCheckbox" />
-<import src="/sky/framework/sky-radio/sky-radio.sky" as="SkyRadio" />
+<import src="/sky/framework/sky-radio.sky" as="SkyRadio" />
 
 <sky-element name="debug-panel">
 <template>
   <style>
   div { display: paragraph; }
   </style>
 
   <sky-box title='Navigation target:'>
     <div><sky-radio group='nav-target' selected='true'
                     on-click="handleRadioDefault"/>Default</div>
@@ skipping 33 matching lines @@
 
   handleCrossAppNavTest(event) {
     this.embedder.navigateTo("http://www.aaronboodman.com/z_dropbox/test.html");
   }
 }.register();
 </script>
 </sky-element>
 
 <debug-panel />
 </sky>