Added variables and lists to classes for future repetition
implementation.

DateEntry
 - repetative dates will be stored as an int using the first seven bits
to determine which days will be repeated, these will be stored in the
new variable repDay
 - additional constructor for repetative events
 
Entry
 - additional constructor for sorting repetative events by the days they
appear on.
 - new method for creating a DateEntry object for rep entries addRep
 
Lister
 - new hashmap the same type as dateList for rep entries called
repeatList
 - new method for adding rep entries called addRep
 
Todo:

- Make a popup window for adding these new type of entries, link it to 
the button that is already present
- Fix the layout, large gaps on the edges
- copy and modify the delete method in Lister to delete rep entries
- Figure out a way to point the delete/edit methods in the Lister to the
correct list for normal and rep entries.
- modify updateList in Lister to add entries found in the repeatList