(TK-35) Clarify limit on number of servers
(TK-35) Clarify limit on number of servers

Make it clear in the jetty-config.md file that the user
is not limited to configuring two servers and can configure
more if desired.

rlinehan/trapperkeeper-webserver-jetty9,puppetlabs/trapperkeeper-webserver-jetty9,camlow325/trapperkeeper-webserver-jetty9,richardc/trapperkeeper-webserver-jetty9,fpringvaldsen/trapperkeeper-webserver-jetty9,fpringvaldsen/trapperkeeper-webserver-jetty9,camlow325/trapperkeeper-webserver-jetty9,puppetlabs/trapperkeeper-webserver-jetty9,rlinehan/trapperkeeper-webserver-jetty9,nwolfe/trapperkeeper-webserver-jetty9,nwolfe/trapperkeeper-webserver-jetty9,richardc/trapperkeeper-webserver-jetty9