Task Validation

- Fixed validation bug whereby recurring child tasks inherited the
  parent status ("recurring") instead of the expected "pending".
- Modified 'add' command to code duplicated in Task::validate.
- Cleaned up associated bug.period.t unit test.

src/recur.cpp

@@ -93,6 +93,7 @@ void handleRecurrence ()
           changed = true;
 
           Task rec (*t);                         // Clone the parent.
+          rec.setStatus (Task::pending);         // Change the status.
           rec.set ("uuid", uuid ());             // New UUID.
           rec.set ("parent", t->get ("uuid"));   // Remember mom.
           rec.setEntry ();                       // New entry date.