Added method update_passenger_starting_address to change the startaddress for a given passenger and event

Reworked passenger construction and renamed passenger creation method in driverrepo to the somewhat awkwardly named get_passenger_and_driver_for_passenger_and_event. It now returns a passenger object which has a reference to a driver object and start_address object

Added logic to event deletion so that it cleans up event/driver and event/passenger associations to prevent foreign key errors
Merge remote-tracking branch 'origin/master'

Conflicts:
	model/driverrepository.py