"Add Star" and "Remove Star" feature for gmail imap client

[Rajiv]

Gmail4j now supports add/remove message flag as starred functionality
for gmail imap client. This new feature can be used used as the
following:

GmailConnection conn = new ImapGmailConnection();
configure connection
GmailClient client = new ImapGmailClient();
client.setConnection(conn);
// to flag a message as starred
client.addStar(message.getMessageNumber());
// to remove star flag from a message flagged as starred
client.removeStar(message.getMessageNumber());

This feature could be used with Gmail4J Next.
see (http://code.google.com/p/gmail4j/issues/detail?id=20)