Review request for JMC-JMC-4057: Adding experimental flame graph view.

[Marcus Hirt]

Hi all,

Please review this change to add an experimental flame graph view.
See known issues in the Jira.

Also cleaning up some imports, and excluding JOverflow from the
development launchers until JMC-6343 is fixed.
 
Jira:   https://bugs.openjdk.java.net/browse/JMC-4057
Webrev: http://cr.openjdk.java.net/~hirt/JMC-4057/webrev.0/

Kind regards,
Marcus