Enhancement - Att::type

- Implemented Att::type to discern attribute types to assist with
  type-specific modifier evaluation.
- Fixed bug that required attributes to have specified values, whereas
  stating "name:" means no value for name.

src/Att.h

@@ -49,6 +49,7 @@ public:
   static bool validNameValue (const std::string&, const std::string&, const std::string&);
   static bool validNameValue (std::string&, std::string&, std::string&);
   static bool validMod (const std::string&);
+  static std::string type (const std::string&);
   void parse (const std::string&);
   void parse (Nibbler&);
   bool match (const Att&) const;