Fix ee10 and ResourceHandler to make them serve jetty-dir.css resource

[lorban]

Jetty version(s) 12

Description

Here's the current state about which of the static content serving mechanisms (ee9 DefaultServlet, ee10 DefaultServlet and ResourceHandler) can serve jetty-dir.css:

	jetty-dir.css
ee9	Y
ee10	N
resource handler	N

As a side note, by design, DefaultHandler is meant to serve favicon while ResourceHandler and both DefaultServlets are supposed to serve only jetty-dir.css.