(a) added absence calendar component plugin to absences tab, (b) we use year from start_date in absences tab for which one to display, default is current year (added im_seconds_from_date and im_year_from_date procs), (c) checks to make sure that we were provided with a single user id in im_absences_calendar_component, (d) component plugin for the absences tab passes empty owner_id if user_selection_type other than "user" and "mine", (e) granted read privileges to employees for both component plugins