Changed the startDate and endDate to LocalDate for easier evaluation and integration. Added a conflictsWithTimeOff method that checks if a date conflicts with a time off, note this doesn't check if it's been approved though.

# Conflicts:
#	SchedulerApp/src/main/java/com/example/schedulerapp/Controller.java
#	SchedulerApp/src/main/resources/com/example/schedulerapp/addShiftPopup.fxml

admin availability null error, can't navigate from staff -> sched (staff loads different panels) pop ups still need to be hooked up

# Conflicts:
#	SchedulerApp/src/main/java/com/example/schedulerapp/Model.java

Fixed some bugs that would cause edited shifts to return nothing, and the edited availability to return nothing.

# Conflicts:
#	SchedulerApp/src/main/java/com/example/schedulerapp/Controller.java
#	SchedulerApp/src/main/java/com/example/schedulerapp/Employee.java