Eliminate dependency on Swing and call to invokeLater

[JaroslavTulach]

There is a support for reporting progress of long running operations via the HeapProgress class. However this class directly calls into AWT which would better be avoided if the librrary is supposed to be used in a headless mode.

This PR keeps the compatibility with existing HeapProgress behavior, yet it avoid the AWT interactions until somebody access HeapProgress.getProgress() model.