Phase II: Cartesian Coordinates

[skutsaev]

Consider switching to Cartesian coordinates. We are currently doing a lot of work and calculations to transform from Cartesian to cylindrical system and backwards.

[bruhwiler]

If we make progress with a port to AMReX, then this will be directly relevant. AMReX supports 2D cylindrical, 2D Cartesian and 3D Cartesian. Hence, the present 3D cylindrical formulation will be difficult to support.