use FormData whenever available
use FormData whenever available

This is an improvement because now forms with
enctype="multipart/form-data" will non break completely
on non-supporting browsers

DanielNeugebauer/adhocracy,alkadis/vcv,phihag/adhocracy,phihag/adhocracy,phihag/adhocracy,liqd/adhocracy,alkadis/vcv,liqd/adhocracy,DanielNeugebauer/adhocracy,phihag/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,alkadis/vcv,alkadis/vcv,DanielNeugebauer/adhocracy,phihag/adhocracy,liqd/adhocracy,liqd/adhocracy,DanielNeugebauer/adhocracy