adding VET i18n messages to marketing toolbox

@marcinpl87 @sebastian-wikia @nandy-andy 

I removed vet_back and vet_close and replaced them with $.msg('vet-back') and $.msg('vet-close') in VET.js, so in this commit https://github.com/Wikia/app/commit/baa90a268cbacde38da9c29fa81da844deb95f28#L7L3 I removed vet_back and vet_close from EditHub.js.  Then I realized those messages weren't actually getting loaded from that file so I added them back in. 

This is a temporary solution until we're done with all VET refactoring.  

I didn't fully test this so please test it and merge this if it works for you.