code cleanup in method getOfferingDetailsForCalendarFeed(): renamed variables, improved code docs, fixed indentation etc.
switched method arguments order to push mandatory arg to the front of the list.
switched argument order when calling getOfferingsDetailsForCalendarFeed() due to method signature changes. provided default value for arg $schoolId.
dropped obsolete method arguments.
WIP: added new method for retrieving ILMs for calendar feeds, and hooked it up to the getData() method of the calendar feed data provider class.