RecHit Based Semi-3D HCAL Clusters

This is the super secret recipe described here:
https://indico.cern.ch/event/324960/contribution/3/material/slides/0.pdf

In this branch the Semi3D clustering is activated by default.

Need to know if I should stick the updated reconstruction into customization function so it only gets applied to some samples? @bachtis

Will rebase to latest 62X IB today.