Added Focused Beam and peek material to Allpix-Squared
I have added a new source type "FOCUSED" to focus beam to a given spot. Used: in config file under [DepositionGeant4] source_type = "focused" focus_point = Xmm Ymm Zmm
Note that beam divergence cannot be used with this new source type.
In addition, I have also added the material "peek" into the material list