MA polling-system: Unclear author

[remco1112]

The polling-system model seems to be first presented in the phd thesis of Mark Timmer (https://doi.org/10.3990/1.9789036505925), but it is unclear whether this is also the source of the files. Currently, the author is Michaela Klauck, but depending on whether Michaela created the file from scratch or converted the files from Mark Timmer, the author might need to be changed to Mark Timmer instead.