Issue #42 - I would like to delete a downloaded picture in the form

[Aporcheron]

Closes issue #42 to delete picture uploaded through the dropzone. 1) Added a route to destroy property image 2) Added a link to this route for the property images which are shows below the dropzone (when the page is reloaded for instance) 3) Added a link to this route in ajax when images are uploaded but the page has not been reloaded (thanks to the option addRemoveLinks defined by Dropzone.js