MATH-837 New method AggregateSummaryStatistics

[Tewfik Zeghmi]

Hi,

I’m not able to aggregate StatisticalSummaryValues.

The ticket has a patch that solves this, but without an update.  How do we get 
Thomas’s patch merged?  It would be very useful.

https://issues.apache.org/jira/browse/MATH-837

Thank you,
Tewfik