Dependencies

- Supports new "depends" attribute.
- Supports "task <id> depends:1,2".
- Supports "task <id> depends:-1,-2".
- Supports id <--> uuid mapping in TDB.

src/Task.h

@@ -73,6 +73,11 @@ public:
   void addAnnotation (const std::string&);
   void removeAnnotations ();
 
+  void addDependency (int);
+  void removeDependency (int);
+  void getDependencies (std::vector <int>&) const;
+  void getDependencies (std::vector <std::string>&) const;
+
   void validate () const;
 
 private: