[SD-4815]: missing labels appearing as empty on content schema editor
[SD-4815]: missing labels appearing as empty on content schema editor

Whenever a translation is missing for an item in the schema of a content
profile, the key for the item is now displayed and a warning to check
the error console for more details.

Do note that whenever adding new items to the schema, subsequent
translations needs to be added in the front-end in
`(superdesk-workspace/content/content.js).ContentProfileSchemaEditor/labelMap`

jerome-poisson/superdesk-client-core,gbbr/superdesk-client-core,fritzSF/superdesk-client-core,ioanpocol/superdesk-client-core,superdesk/superdesk-client-core,darconny/superdesk-client-core,Aca-jov/superdesk-client-core,petrjasek/superdesk-client-core,lnogues/superdesk-client-core,darconny/superdesk-client-core,mscam/superdesk-client-core,lnogues/superdesk-client-core,ioanpocol/superdesk-client-core,superdesk/superdesk-client-core,fritzSF/superdesk-client-core,jerome-poisson/superdesk-client-core,marwoodandrew/superdesk-client-core,thnkloud9/superdesk-client-core,thnkloud9/superdesk-client-core,ioanpocol/superdesk-client-core,petrjasek/superdesk-client-core,mdhaman/superdesk-client-core,gbbr/superdesk-client-core,lnogues/superdesk-client-core,mscam/superdesk-client-core,mugurrus/superdesk-client-core,fritzSF/superdesk-client-core,mdhaman/superdesk-client-core,mugurrus/superdesk-client-core,pavlovicnemanja/superdesk-client-core,mdhaman/superdesk-client-core,fritzSF/superdesk-client-core,superdesk/superdesk-client-core,thnkloud9/superdesk-client-core,mscam/superdesk-client-core,superdesk/superdesk-client-core,jerome-poisson/superdesk-client-core,mdhaman/superdesk-client-core,superdesk/superdesk-client-core,thnkloud9/superdesk-client-core,pavlovicnemanja/superdesk-client-core,mscam/superdesk-client-core,pavlovicnemanja/superdesk-client-core,marwoodandrew/superdesk-client-core,gbbr/superdesk-client-core,pavlovicnemanja/superdesk-client-core,marwoodandrew/superdesk-client-core,jerome-poisson/superdesk-client-core,ioanpocol/superdesk-client-core,pavlovicnemanja/superdesk-client-core,darconny/superdesk-client-core,mdhaman/superdesk-client-core,gbbr/superdesk-client-core,marwoodandrew/superdesk-client-core,Aca-jov/superdesk-client-core,marwoodandrew/superdesk-client-core,Aca-jov/superdesk-client-core,ioanpocol/superdesk-client-core,darconny/superdesk-client-core,mugurrus/superdesk-client-core,mugurrus/superdesk-client-core,jerome-poisson/superdesk-client-core,lnogues/superdesk-client-core,petrjasek/superdesk-client-core,Aca-jov/superdesk-client-core,petrjasek/superdesk-client-core,petrjasek/superdesk-client-core