Debris basin flow routing

This should be added to the DEM module, as this is ultimately a TauDEM routine. The output (upslope_basins?) can be passed to the "segments" module later, analogously to how total_area and burned_area are passed to the stream module.

There will now be 3 computations that rely on the upslope_area routine, so it may be worth aliasing commands for total_area, burned_area, and upslope_basins(?). In particular, upslope_basins is a rather non-intuitive use case, so we should at least include it as a separate command.

Finally, debris basins should be added as an optional argument to the operational analysis routine.