LibWeb: Start implementing basic JavaScript DOM bindings

This patch introduces the Wrapper and Wrappable classes.

Node now inherits from Wrappable, and can be wrapped in a GC-allocated
Bindings::NodeWrapper object. The only property we expose right now is
the very simple nodeName property.

When a Document's JS::Interpreter is first instantiated, we add a
"document" property with a DocumentWrapper object to the global object.

This is pretty cool! :^)

Libraries/LibWeb/Forward.h

@@ -34,4 +34,14 @@ class Frame;
 class HtmlView;
 class Node;
 
+namespace Bindings {
+
+class DocumentWrapper;
+class NodeWrapper;
+class Wrappable;
+class Wrapper;
+
+}
+
+
 }