Added TaskType enumeration to determine the task type
->  TYPE_FLOATING
->  TYPE_DEADLINE
->  TYPE_TIMED
Changed the implementation of Command class from Interface to abstract.
-> Command will store task object
updated Command algorithm
Change task attribute from calendar to LocalDateTime
Change LocalDateTime to LocalDate and LocalTime to separate the date from the time
Completed UndoHandler
Completed UndoHandler ( Not tested )
Completed all undo implementation for Commands