Restart for Plugin BinEnergyParticles

The old text file is opened, filtered for previous values and pre-pended to the new file during restarts.

The old implementation made a manual copy-and-join of the output necessary (see note <sup>1</sup> in the [wiki](https://github.com/ComputationalRadiationPhysics/picongpu/wiki/PIConGPU-Plugins)).

### To Do

- [ ] perform a run time test
Why does this function return `writeToFile`. This seems odd, as its return code is never used and `writeToFile` is a class member.