ExplicitRungeKutta time integrators is ignoring ghosts
ExplicitRungeKutta time integrators is ignoring ghosts. It must at least use CartesianDiscreteFieldGhostExchanger on K[i] when i>0 otherwise all but first call to RHS is using wrong values for Xtmp on domain edges if ghosts exists. Final ghosts update on Xout should be deffered to calling operator.