rem: KNHeaders::MessageID* messageID(bool create=true) { if(!create && m_essageID.isEmpty()) return 0; return &m_essageID; }
add: virtual KNHeaders::MessageID* messageID(bool create=true)        { KNHeaders::MessageID *p=0; return getHeaderInstance(p, create); }
context:     KNHeaders::MessageID* messageID(bool create=true) { if(!create && m_essageID.isEmpty()) return 0; return &m_essageID; }