Add possibility to set content-disposition header for binaries by mimetype, so that the browser will show a popup instead of display the binary file inline

If you click on a link that leads to a binary file, now the browser will perform an action based on the selected mime-type configuration for the current operating system. By means of the content-disposition header you can enforce the browser to display a popup, which gives the user a choice if he wants to download or save the current attachment.

Patch provided by Tom van Zummeren (JTeam)