DetectorHistogrammer: allow smearing by track resolution
Allow smearing of the Monte Carlo truth position in the sensor with some track resolution.
This MR is very simple but there is one "issue" that I was too lazy to work around properly: we use the particle position in two loops (once over all clusters, once over all particles). Currently, I do two independent convolutions of the position, so the two "measurements" are not equal anymore. While not being fully correct, it is a bit annoying to solve because we would have to calculate smeared positions for all MC particles, store it alongside the particle and then use it - not very nice.