Additions to DoubleMatrixDataSet
Speed up of multithreaded correlation and addition of multithreaded covariation

Added tests for descriptives and correlation tasks
Merge branch 'master' of https://github.com/molgenis/systemsgenetics
Merge branch 'master' of https://github.com/molgenis/systemsgenetics
Merge pull request #26 from Bonder-MJ/master

Additions to DoubleMatrixDataset, addition of mulitthreaded covariation calc, speed up of multithreaded correlation calculation