rework JMX model

Currently on refresh each node is recreated as a different object instead of just reloading its data. This causes problems with the JMX navigator tree and ends up in collapsing all nodes on refresh on a sub node which is really annoying. The whole model should be reworked to only wrap the JMX data and on refresh stay the same object but with refreshed jmx data. That way the tree should behave normal again.