introduce web_components pkg for consolidated polyfills

pkg/html_import/lib/html_import.debug.js

-/* 
- * Copyright 2013 The Polymer Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style
- * license that can be found in the LICENSE file.
- */
-
-(function() {
-  
-var thisFile = 'html_import.debug.js';
-var scopeName = 'HTMLImports';
-var modules = [
-    'src/Parser.js',
-    'src/HTMLImports.js',
-    'src/boot.js'
-];
-
-// export 
-
-window[scopeName] = {
-  entryPointName: thisFile,
-  modules: modules
-};
-
-// bootstrap
-
-var script = document.querySelector('script[src*="' + thisFile + '"]');
-var src = script.attributes.src.value;
-var basePath = src.slice(0, src.indexOf(thisFile));
-
-if (!window.Loader) {
-  var path = basePath + 'tools/loader/loader.js';
-  document.write('<script src="' + path + '"></script>');
-} 
-document.write('<script>Loader.load("' + scopeName + '")</script>');
-  
-})();