Make to and from addresses settable from web ui

[ilmaisin]

Curretly this driver gets the to and from addresses from manually defined lpoptions mailfrom and mailto. This is however not a very good user experience. Starting from CUPS 1.3, it has been possible to have PPD files accept arbitary strings as configuration options, but the syntax is confusing to me.

Another option would be to have a separate configuration file like CUPS-PDF has, but that would again be inferior to the former option in what it comes to user experience.

[ilmaisin]

This probably should be done by parsing the PPD file that's path is provided in the PPD environment variable.