Allpix2 Module for fast simulation

An Allpix2 module that wraps around the fast simulation created in #3. The goal is to use the (soon-to-be-)existing framework (see #1) to create validation plots of the implementation

It should be enough to create a replacement for the GenericPropagation module (FastMalta2Propagation?) and keep rest of the Allpix2 configuration the same.