Annotation Bug

- Fixed DOM lookup of special-case attributes: id and urgency are
  not stored in the usual manner, and must be handled differently.
- Removed the responsibility of DOM to evaluate literals, because
  they are handled more effectively in A3::tokenize.
- Fixed old code that assumed ".id" instead of "id".
- Removed unnecessary diag call from annotate.t.

src/DOM.h

@@ -43,9 +43,6 @@ public:
   const std::string get (const std::string&, const Task&);
   void set (const std::string&, const std::string&);
 
-private:
-  bool is_literal (std::string&);
-
 private:
   std::map <std::string, std::string> _cache;
 };