Bug 1330900 - Implement <script nomodule>

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

Tag #618

dom/html/HTMLScriptElement.h

@@ -89,6 +89,8 @@ public:
   }
   bool Async();
   void SetAsync(bool aValue, ErrorResult& rv);
+  bool NoModule();
+  void SetNoModule(bool aValue, ErrorResult& rv);
 
 protected:
   virtual ~HTMLScriptElement();