Building WarpX to use RZ geometry

WarpX can be built to run with RZ geometry. Currently, this only allows pure axisymmetry (i.e. mode 0) with an FDTD solver.

To select RZ geometry, set the flag USE_RZ = TRUE when compiling:

make -j 4 USE_RZ=TRUE

Note that this sets DIM=2, which is required with USE_RZ=TRUE. The executable produced will have “RZ” as a suffix. Currently does not work with USE_PSATD.