[INGEST] added an option to skip iptc_codes processing
[INGEST] added an option to skip iptc_codes processing

process_iptc_codes was causing trouble with NTB (see SDNTB-344
comments), this commit add an "INGEST_SKIP_IPTC_CODES" option to skip
this processing.

This is a temporary solution, a better option should be applied using
some extensions mechanism like hooks (SDESK-439).

needed for SDNTB-344

superdesk/superdesk-core,superdesk/superdesk-core,ioanpocol/superdesk-core,petrjasek/superdesk-core,ancafarcas/superdesk-core,mdhaman/superdesk-core,mdhaman/superdesk-core,ioanpocol/superdesk-core,hlmnrmr/superdesk-core,petrjasek/superdesk-core,petrjasek/superdesk-core,superdesk/superdesk-core,mugurrus/superdesk-core,mugurrus/superdesk-core,petrjasek/superdesk-core,nistormihai/superdesk-core,marwoodandrew/superdesk-core,marwoodandrew/superdesk-core,superdesk/superdesk-core,ioanpocol/superdesk-core,nistormihai/superdesk-core,mugurrus/superdesk-core,mdhaman/superdesk-core,ancafarcas/superdesk-core,hlmnrmr/superdesk-core