Update jetty-client, jetty-server, ... to 9.4.15.v20190215
Update jetty-client, jetty-server, ... to 9.4.15.v20190215

rossabaker/http4s,ChristopherDavenport/http4s,rossabaker/http4s,aeons/http4s,aeons/http4s,ChristopherDavenport/http4s,ChristopherDavenport/http4s,http4s/http4s,aeons/http4s