Add more session doc

jetty-documentation/src/main/asciidoc/administration/sessions/chapter.adoc

@@ -25,6 +25,7 @@ Jetty also offers more niche session managers that leverage backends such as Mon
 
 include::session-hierarchy.adoc[]
 include::sessions-details.adoc[]
+include::session-configuration-memory.adoc[]
 include::session-configuration-file-system.adoc[]
 include::session-configuration-jdbc.adoc[]
 include::session-configuration-mongodb.adoc[]

jetty-documentation/src/main/asciidoc/administration/sessions/session-configuration-memory.adoc

@@ -0,0 +1,39 @@
+//  ========================================================================
+//  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
+//  ========================================================================
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+
+[[configuring-sessions-memory]]
+
+=== Non-Clustered Session Management: Memory
+
+Non-clustered, in-memory-only is the default style of session management.
+In previous versions of jetty this was referred to as "hash" sessions, as they were stored in a HashMap in  memory.
+When using the Jetty distribution, if you do not configure any session module, this will be enabled by default.
+
+Specifically, jetty will hook up:
+
+[horizontal]
+*a DefaultSessionIdManager*::
+- produces unique session ids and supports cross-context dispatch re-use of session ids
+*a HouseKeeper*::
+- scavenges expired sessions every 10 mins
+*a DefaultSessionCache per context*::
+- keeps session objects in memory
+*a NullSessionDataStore per context*::
+- no persistence of sessions
+
+
+If you wish to change any of the default configuration, enable the *session-cache-hash* module.
+

jetty-documentation/src/main/asciidoc/reference/upgrading/upgrading-9.3-to-9.4.adoc

@@ -128,7 +128,7 @@ The new default provides similar features to the old hash session management:
 Requests for the same session in the same context share the same session object.
 Session objects remain in the cache until they expire or are explicitly invalidated.
 
-If you wish to configure the default setup further, enable the `session-cache-default` module.
+If you wish to configure the default setup further, enable the `session-cache-hash` module.
 
 *Compatibility*