Snooping clean (#4565)

* initial commit

* updating header with new function name

* small clean

* initial add of DS test statistics to BundleObservation

* addressing comments I

* addressing comments II

* addressing comments III

* Null initialized pointers

* Initialize null pointers in header

* Remove null initialize in constructor

Co-authored-by: Jesse Mapel <jmapel@usgs.gov>