(PE-2790) Fix for Jetty always opening binding for a plain http port

Prior to this commit, Jetty would always open a binding for an http
port, whether or not a "port" value was actually specified in the
webserver config for the service.

With the changes in this commit, an http port binding is only created if
one is specified in the webserver config.
If neither port nor ssl-port is specified in the webserver config, throw
an IllegalArgumentException from configure-web-server in
jetty9_config.clj.  Also fixed test that was previously failing due to
not accounting for the port no longer being implcitly set by the service
library.
Added a .gitignore and a CHANGELOG.md.  The CHANGELOG.md documents the
http port binding change.
Merge pull request #5 from camlow325/feature/master/PE-2790-jetty-always-opens-plain-http-port

(PE-2790) Fix for Jetty always opening binding for a plain http port