new detector for vulnerable Jetty Servers

[kjlubick]

From mebigfatguy#15

I recently ran into an exploit that depended on the following snippet:
https://gist.github.com/kjlubick/560dda55c47dd3a53643

The problem was that I meant to make a local server that was only accessible to the local machine, but instead, because I didn't specify otherwise, the port was open to everyone on the local network.

I'm proposing a relatively simple detector that looks for a Jetty server (and possibly other flavors) that is created by only specifying the port number, thereby making them vulnerable to snooping via network.

One topic for discussion is avoiding false positives when the intent is to make a local network server. This could possibly be done by having a whitelist of ports (e.g. port 80) that are not flagged as a bug.

We'll start with the whitelist of 80 and 8080, which are known to be commonly used for external web servers.