code: public Priority setPriority(Integer priority) {
  		Priority prop = (priority == null) ? null : new Priority(priority);
  		setPriority(prop);
  		return prop;
  	}
docs: Sets the priority of the event.
  @param priority the priority ("0" is undefined, "1" is the highest, "9"
  is the lowest) or null to remove
  @return the property that was created
  @see <a href="http://tools.ietf.org/html/rfc5545#page-89">RFC 5545
  p.89-90</a>
  @see <a href="http://tools.ietf.org/html/rfc2445#page-85">RFC 2445
  p.85-7</a>
  @see <a href="http://www.imc.org/pdi/vcal-10.doc">vCal 1.0 p.33</a>