TCAD simulation of a Malta2-like sensor

The Allpix2 simulation should be made more realistic by using Synopsis TCAD to calculate the electric field of a small collection electrode MAPS sensor with the p-wells, n-implant and p-bulk in roughly the right places.

The work should revolve around creating a new Allpix2 steering file, where the calculated meshes and weighting fields are loaded by Allpix2 using the ElectricFieldReader and WeightingPotentialReader. No extra development should be needed.

The results can be quickly validated by looking at the efficiency maps calculated using the normal reconstruction software. This depends on #1. The tuning of the TCAD simulation to improve match with data is for another issue,.