Add utility to capture histograms after GC

[zolyfarkas]

Should allow for trending object instances... The JVM can print this out, stdout can be captured automatically, data parsed and stored in a TSDB. Data can then be visualized with the UI, new functionality will probably be required...

capture proof of concept in: https://github.com/zolyfarkas/spf4j/blob/master/spf4j-experimental/src/test/java/org/spf4j/perf/memory/VMHistogramsTest.java