[NITF] [FORMATTER] use new specification for subject
[NITF] [FORMATTER] use new specification for subject

"subject" meta element now uses the new specifications with a nyX-
prefix for article updates.

SDNTB-254

superdesk/superdesk-ntb,petrjasek/superdesk-ntb,superdesk/superdesk-ntb,ioanpocol/superdesk-ntb,ioanpocol/superdesk-ntb,petrjasek/superdesk-ntb,petrjasek/superdesk-ntb,petrjasek/superdesk-ntb,ioanpocol/superdesk-ntb,superdesk/superdesk-ntb,superdesk/superdesk-ntb