Add all supported JVM JMX metrics to default JSON file

[myllynen]

Using https://github.com/myllynen/mbean2json we saw:

With the newly generated jvm.json the number of available metrics jumps from 18 (that are available with the default jvm.json) to 147. Metric names and descriptions are based on a simple generator so if there's anyone wanting to put this in, all metrics names and descriptions should be reviewed and adjusted as needed.

Issue #46 and #47 are relevant as well when updating the default jvm.json.

Thanks.