Simplify spherical quick_index and kde reconstruction#1123

Merged

KineticTheory merged 4 commits intolanl:developfrom clevelam:fix_sphere_kde

Aug 27, 2021

+1,376-1,262

Commits on Aug 26, 2021

rely on quick_index for spherical reconstruction
Cleveland
committed
regression cleanup
Cleveland
committed
locations can remain non-mutable
Cleveland
committed

Commits on Aug 27, 2021

fix overlap sign error
Cleveland
committed