title: Add translation variable to prestashop 1.7
body: <p>I have a question concerning Prestashop 1.7 translation variables.</p>
  
  <p>Actually, "<strong>how to add translation variable to Prestashop</strong>"?
  I need only some translation variables <strong><em>I can modify(content) then in BO</em></strong> (International>Translations>than I can modify the content of variable)</p>
  
  <p>Thanks a lot!</p>