Code Migration

- Migrated taskd JSON parser into task, to provide encode/decode
  capability to Task::composeJSON.
- Migrated taskd utf8 code, replacing old unused code.
- Added unit tests or JSON.
- Migrated Tree updates from taskd.

src/Tree.h

@@ -47,9 +47,11 @@ public:
   void replaceBranch (Tree*, Tree*);
   int branches ();
 
+  void name (const std::string&);
   std::string name () const;
   void attribute (const std::string&, const std::string&);
   void attribute (const std::string&, const int);
+  void attribute (const std::string&, const double);
   std::string attribute (const std::string&);
   void removeAttribute (const std::string&);
   int attributes () const;