Enhancement - Path integration

- Implemented Path::operator (std::string) const, to provide an
  automatic cast to std::string for any Path, File or Directory.
- Made use of new cast in various code.
- Changed use of spaces in atoi () calls.
- Switched from std::string::data () to std::string::c_str () calls.

src/Path.h

@@ -39,6 +39,8 @@ public:
   virtual ~Path ();
 
   Path& operator= (const Path&);
+  operator std::string () const;
+
   std::string name () const;
   std::string parent () const;
   std::string extension () const;