Slide Log: SIMULATION_STATE and only of affected

This change reduces some noise in stdout.

- use `SIMULATION_STATE` for output log class
- only trigger log if performing a slide (last plane)

I removed some end-of-line white spaces, too. You might enjoy the [minimal diff](https://github.com/ComputationalRadiationPhysics/picongpu/pull/354/files?w=1).