Introduce the DEFAULT IfcWorkCalendarTypeEnum that indicates the default schedule Calendar

Many scheduling tools have a concept of defining the default schedule calendar. The default schedule calendar could be used for task relation lag calculation (in case that IfcTaskDurationEnum.WORKTIME is set to IfcRelSequence) or for assigning the calendar to newly created tasks in scheduling tools.
The IfcWorkCalendar already contains the PredefinedType attribute. In order to enable the preserving of this information, it’s needed to add the DEFAULT value to the IfcWorkCalendarTypeEnum.