CASA 6 cube imaging refactor

This page is for tracking the testing of the CASA 6 cube refactor documented here:

https://docs.google.com/document/d/1Jv-t_4k5Vv1Rgh_eYeU4j84UWrrnO3d6INLBFtuMD6s/edit?usp=sharing

There are two primary goals to our tests:

1. Demonstrate that the refactored code has the desired memory footprint effect.  We'll start with the referenced data set and then expand to larger data sets.  
2. Demonstrate the runtime cost of the refactored code and whether it's a fixed overhead so it's contribution goes to zero for larger data sets or whether the overhead scales with image complexity