Update ZDC Implementation

• one silicon pad + one layer of PbWO4) + (Pb+Silicon) + (Pb+Sci + additional 8 layers
• some space (~10cm) between the (PbWO4) and the (PbSilicon) for the PMTs
• PbWO4 ~$1.5M, Pb+Silicon ~$1M, and then the Pb+Sci ~ $800k