code: public Uid setUid(String uid) {
  		Uid prop = (uid == null) ? null : new Uid(uid);
  		setUid(prop);
  		return prop;
  	}
docs: Sets the unique identifier for this journal entry. This component object
  comes populated with a UID on creation. This is a <b>required</b>
  property.
  @param uid the UID or null to remove
  @return the property that was created
  @see <a href="http://tools.ietf.org/html/rfc5545#page-117">RFC 5545
  p.117-8</a>
  @see <a href="http://tools.ietf.org/html/rfc2445#page-111">RFC 2445
  p.111-2</a>