added DataStore.updateCurrentTask()

DataStore.py

@@ -64,3 +64,16 @@ WHERE id = 0
         c.close()
         self.conn.commit()
         return ct
+
+    def updateCurrentTask(self, ct):
+        c = self.conn.cursor()
+        c.execute('''
+DELETE FROM history
+WHERE id = 0
+''')
+        c.execute('''
+INSERT INTO history
+VALUES (0, ?, ?)
+''', (ct.taskid, ct.dt.strftime(HISTORY_DT_FMT)))
+        c.close()
+        self.conn.commit()