Make the VisiTor scripts accept more web log formats

The VisiTor scripts (both Java and Python) parse a web server log and the exit list archives to tell how many of the requests come from Tor users. They currently require Apache's combined log format ("%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"") as input. If users have a different format, they need to transform their log to said format before passing it to VisiTor.

We should also support Apache's common log format ("%h %l %u %t \"%r\" %>s %b"). This format doesn't have the User-agent string and can therefore not detect Torbutton users. But knowing whether users connect via the Tor network, with or without Torbutton, can still be a useful result.

Are there further commonly used web log formats that we should support?

Setting priority to minor, because I haven't heard of many VisiTor users lately.