Allow setting of Jetty Connector accept queue size

Allow setting of Jetty Connector accept queue size. This works in conjunction with OS level sysctls net.core.somaxconn and net.ipv4.tcp_max_syn_backlog.

My understanding, based on the documentation and inspecting the running code, is that Jetty defaults the accept queue size of a Connector to 0, which trickles down to mean that the actual queue size as enforced via Java's ServerSocket will be 50.

http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/server/ServerConnector.html
http://docs.oracle.com/javase/7/docs/api/java/net/ServerSocket.html#ServerSocket%28int%29

The way I'm getting at the Connector here may be a little hacky; I'm not sure (assuming there will be only 1, most notably). I also have almost no experience with Jetty, so while these changes appear to be working (both not blowing up, and actually achieving their purpose), if you are suspicious of what I am doing here you have every right to be.
    
Note that these changes were branched from master, which still includes the Keep-Alive response header in the wrong place as discussed in the comments of pull request 2.