dialog: do not print missing to tag error for final replies in DLG_STATE_UNCONFIRMED
pua: define constants for send_publish return codes
pua_dialog_info: failed calls should not trigger PUBLISH errors
 - related to Issue #142
pua_dialoginfo: documentation updates
dialog: print dialog start and timeout in human readable format (MI)
Fix "mf_process_maxfwd_header" retcode in case of parsing errors