Bug 1330900 - Implement <script nomodule>, r=bz

This patch implements:
. noModule getter/setter for HTMLScriptElement
. the nomodule attribute for HTMLScriptElement
. and the logic in nsScriptLoader that denies the loading of a nomodule script
. with tests

dom/html/HTMLScriptElement.h

@@ -90,6 +90,8 @@ public:
   }
   bool Async();
   void SetAsync(bool aValue, ErrorResult& rv);
+  bool NoModule();
+  void SetNoModule(bool aValue, ErrorResult& rv);
 
 protected:
   virtual ~HTMLScriptElement();