Bug 392371 - JavaUtilLog performing expensive format for unlogged items

* Adding isLoggable checks where format() is used
jetty-9 ignore closeable DOS test for now
jetty-9 use spare space in content buffer for header
396460 Make ServerConnector configurable with jetty-maven-plugin
396473 JettyWebXMlConfiguration does not reset serverclasses
396472 org.eclipse.jetty.websocket needs to be removed from serverclasses as it should only be a systemclass
396475 Remove unneeded websocket-server dependency from test-jetty-webapp
396474 add websocket server classes to jetty-maven-plugin classpath
Revert "jetty-9 added null constructor"
Introduced Response.HeaderListener to allow applications to control processing of headers.
396518 - Websocket AB Tests should test for which side disconnected and closed.wasClean

* Adding stubbed out example in Fuzzer for wasClean.
Introduced HttpCookieStore.Empty to disable cookies in HttpClient and in the websocket client.
add in some handshake state tracking into IOState to help track who initiated closes
Introduced Request.CommitListener to separate the pre-commit request event from the commit request event.
396518 - Websocket AB Tests should test for which side disconnected and closed.wasClean

+ adding AbstractWebSocketConnection.onWriteWebSocketClose() to allow
  for different behavior between client vs server TCP disconnect logic.
Removing test for inputClosed on BlockheadClient to fix test failure.
jetty-9 use spare space in content buffer for header
jetty-9 use spare space in content buffer for header
jetty-9 optimisation to dispatch before parsing so that handling is done in same thread
Merge remote-tracking branch 'origin/jetty-8'

Conflicts:
	jetty-util/src/main/java/org/eclipse/jetty/util/MultiPartInputStream.java
	jetty-util/src/test/java/org/eclipse/jetty/util/MultiPartInputStreamTest.java