Added new methods to Task object

New methods added:
displayStartDate()
displayStartTime()
displayEndDate()
displayEndTime()
displayDate()
displayTime()

Why is this change necessary?
- These extra methods return only the date and only the time. It is
  necessary to parse the date and the time separately in
  GoogleCalendarManager, because of the way google APIs work.

How does it address the issue?
- By adding these new methods, GoogleCalendarManager is able to call the
  task object, and directly obtain the values, without the need to edit
  the string within GoogleCalendarManager itself.