Enhancements - Cmd object

- New Cmd object to handle localized commands, customReports and general
  command parsing.
- Localized new Subst methods.
- Relocate guess method from parse.cpp to text.cpp.
- Converted Att object to use new valid/parse scheme.
- Unit tests for Cmd object.
- Fixed att.t.cpp unit tests.

src/Att.h

@@ -41,7 +41,8 @@ public:
   Att& operator= (const Att&);                  // Assignment operator
   ~Att ();                                      // Destructor
 
-  bool parse (Nibbler&);
+  bool valid (const std::string&) const;
+  void parse (Nibbler&);
   bool validMod (const std::string&) const;
   bool match (const Att&) const;