Task

- Improved structure of legacy duration value upgrades, so it can be used for
  other things, namely UDA durations.

src/Task.h

@@ -163,6 +163,7 @@ private:
   void validate_before (const std::string&, const std::string&);
   const std::string encode (const std::string&) const;
   const std::string decode (const std::string&) const;
+  void upgradeLegacyValue (std::string&);
 
 public:
   float urgency_priority () const;