Make Jetty Server lazy

JettyServerModule had been eagerly instantiating the Server object, which was causing things that didn't care about an HTTP interface to all of a sudden require host and port parameters.  The change makes the JettyServerModule only setup the bindings without eagerly instantiating the Jetty Server.  Each cli needs to register the Server class with the Lifecycle in order to make it actually get used.
Move docs into a separate directory to better facilitate the separation that will exist.  I think.
Add missed com.metamx.druid.emitter.period propery to ConvertProperties