Jetty / servlet JARs not packaged for monitor

The monitor needs Jetty (and, transitively, the servlet API) to run. The tarball generated by mvn -P assemble package does not include Jetty, so an installation needs to get it from elsewhere.

ACCUMULO-2301 was the first attempt at fixing this, and it works for 1.4 and 1.5, but it appears that the change didn't make it to 1.6.

A workaround is to hand-copy the Jetty and servlet JARs to Accumulo's lib directory, or add a location where Jetty already exists to the Accumulo classpath.