#2 Remove statistic_file from povray-options

[Tobias Ellinghaus]

In the moment the server sends statistic_file as a
povray option although the client doesn't accept it
since it isn't whitelisted.
The only problem in the moment is that it results in
a message telling that it found an illegal option.
In order to remove that option we would have to
change frame-get.pl and impsub.pl since it's added to
the HMAC-digest.