fix(FallFlavours): save items to vault with respect to eventNum

Constructor saves items from file to the spot of vault based on
eventNum. If constructor finds that current spot is already taken, it
replaces element at that spot
feat(FallFlavours): add search FallEvents by description and category
style(ast01-PartB): change tabbing to 2 spaces instead of 4
feat(FallFlavours): add listAllEvents method
feat(FallFlavours): add methods to add and delete events

Added public methods into FallFlavours class to add new events to vault
based on event number and to delete old events from vault.