Integration - TDB write operations

- TDB::gc rewritten.
- TDB::commit fixed.
- Corrected usage of handleRecurringTasks wrt TDB.
- Unit tests for TDB.

src/main.h

@@ -45,7 +45,7 @@ void gatherNextTasks (std::vector <Task>&, std::vector <int>&);
 void onChangeCallback ();
 
 // recur.cpp
-void handleRecurrence ();
+void handleRecurrence (std::vector <Task>&);
 Date getNextRecurrence (Date&, std::string&);
 bool generateDueDates (Task&, std::vector <Date>&);
 void updateRecurrenceMask (/*TDB&,*/ std::vector <Task>&, Task&);