some refactoring
Big refactoring, new tools integration

Added Handlebars and i18n to deal respectively with templating and internationalization.

CreatorField is currently the only custom input to be fully working with these new tools.
updated LanguageValueField and IdentifierField
Merge branch 'master' of github.com:medialab/reference_manager
Every inputs - except for DocumentField - have been updated (i18n, handlebars)