Publish button

[Frolipon]

We need a new button "Publish", in the same fashion as the "Download" or "FTP" button.

The "Publish" button should do the same thing as the FTP button :

• Push the images on a distant FTP
• Replace the path of the images
  But instead of downloading a zip file with the HTML, the HTML should be published on a FTP.

Each push on the "Publish" button should update the same HTML on the FTP.

The idea is to allow the users to update an existing email directly in Le Patron, without having to re-upload the email in the ESP. The ESP will only be given the publish URL to get the HTML.