CaloTPCnv: Support MT thinning.
Extend CaloCellPacker_400_500 and CaloCompactCellTool to handle MT thinning. The pack interfaces now take a ThinningDecisionBase object. Extend CaloCellContainerCnv_p1 to retrieve and pass the ThinningDecisionBase object. Extend CaloCellLinkContainerCnv_p2 to handle MT thinning.