452188 Delay dispatch until content optimisation.

Renamed property "delayDispatchUntilContent".
452516 - Make HttpOutput aggregation size configurable.

Introduced new property "outputAggregationSize" in HttpConfiguration,
and correspondent property in XML file.
improved debugging
ignore bad test
443652 - Remove dependency on java.lang.management classes

* Created safer Uptime singleton for use
* Removed direct references to java.lang.management from
   - Server.java
   - Log.java
   - AbstractLifeCycle.java
Merge branch 'jetty-9.2.x'

Conflicts:
	jetty-server/src/main/config/etc/jetty.xml
	jetty-server/src/main/config/modules/server.mod
	jetty-server/src/main/java/org/eclipse/jetty/server/HttpChannel.java
	jetty-server/src/main/java/org/eclipse/jetty/server/HttpConfiguration.java
	jetty-server/src/main/java/org/eclipse/jetty/server/HttpConnection.java
	jetty-server/src/main/java/org/eclipse/jetty/server/HttpOutput.java