add submit form tag 

Name : ja_submit
call in twig(example) : {{ ja_submit({'url': path('homepage'), 'dataType' : 'json', 'type': 'POST', 'success' : 'console.log("ok")', 'text' : 'valider', 'class' : 'sf-button'}) }}
Merge pull request #1 from bmustapha/patch-1

add submit form tag