Implemented the fastest way to calculate the dw structure.
This uses the numpy ufunc multiply.outer function to create the outer array, and then multiply with the frqs_structure.
Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.
Authored by: tlinnet 2014-06-11
Parent: [r23827]
Child: [r23829]
