Fix type conversion for deposits causing peak shifts (GH PR 43)
Type conversion for number of charges creation during deposition truncated the result, causing bias to lower energies. This resulted in a peak shift towards lower energies. To fix this, the number of charges created is instead rounded to the nearest integer. Further details are explained here: https://allpix-squared-forum.web.cern.ch/t/charge-creation-type-conversion-introduces-peak-shift-to-lower-energies/405