Helper functions

- Rescued the ::encode and ::decode funtions and put them in util.cpp.
  This is because 2.0 will still need to perform the same encode/decode
  operations without Att.cpp around.

src/util.h

@@ -85,5 +85,8 @@ void combine (std::vector <int>&, const std::vector <int>&);
 
 unsigned burndown_size (unsigned ntasks);
 
+const std::string encode (const std::string&);
+const std::string decode (const std::string&);
+
 #endif
 ////////////////////////////////////////////////////////////////////////////////