made entire server safe by try-catching all send and database actions,
also returns proper enum values for success / failure
adds method for fetching all users with their appointments, and refactured
insert to generate connections based on participating list, and not
creator_id
removed pink
access control for edit, create, and delete of appointments
added enum actions
abstractmodel now implements serializable
constructor for callback
meetingpoint now implements abstractmodel
user now overrides compare / hashing & fixed copy-constructor
appointment overrides equals and hashcode, copyconstructor now copies users properly
refactured login check
removed unneded parameter
cleaned up notification
alarm now implements abstractmodel and nessecary methods
rewrite of login function, all events are now saved in hash with their
respective users as keys, rewrote add/delete/update appointments to use
callbacks + use the new hash structure
addparticipants now show up in their respective columns
removed comment