If form is enctype="multipart/form-data", send data as a FormData object, else serialize the form
Merge branch 'master' of git://github.com/AppVentus/AvAjaxBundle

# By Loïc Goyet
# Via Leny BERNARD (2) and Loïc Goyet (1)
* 'master' of git://github.com/AppVentus/AvAjaxBundle:
  new ajax witness in full css