before addressing divide by zero bug
Didn't fix bug yet need to reoptimize code first
In progress, reworking grid system to use logarithmically spaced r_mid. working on walker next
Commit before branching to redo LOS
Initial indices and step direction determined.
Stalled progress on cylindrical grid
Cartesian grid and walker seem to work
Merge branch 'cartesian_grid'

Bringing Cartesian feature into master