Fixed error with addMeetingNotes(), which caused found pastMeetings to throw an error. Fixed by putting a return statement in once a pastMeeting has been found.
Fixed positioning of first return statement in addMeetingNotes() method that was causing it to exit prematurely.
Now implements Comparable to facilitate the sorting of contacts by ID number when required (e.g. in displayContactList() in ContactManagerUtilties).
Corrected casting in loadData() so that objects read from file are cast to their interface rather than implementation. Corrected other minor errors and typos.
displayContactList() method now prints contacts sorted by ID number, with the use of a TreeSet. This is far more helpful than the jumbled mess that used to be displayed before. This method is now used by selectAttendees() in this class, to avoid code repetition.