Issue67 radiator

Merge the radiator from the `Buildings` library to the `Annex60` library.

The radiator is needed for the benchmarks that @nytschgeusen is working on.

This merge already incorporates the changes of `issue65_syncBuildings`. Hence, I suggest to first merge #66 to the master.

I already merged the radiator to `issue45_benchmarks` so that @nytschgeusen can use it without having to load the `Buildings` library.