improve constructor/view_days.vim, constructor/view_months.vim, event/local.vim, google/calendar.vim, view/event.vim, view/month.vim: use join(d.get_ymd(), '-') instead of printf for event key (for performance)
improve constructor/view_days.vim, event.vim, event/local.vim, google/calendar.vim, view/month.vim: remove moonIndex, daynumIndex, weeknumIndex and holidayIndex