Finish consumes for Validation/MuonCSCDigis

I thought I'd completed adding consumes interface to Validation/MuonCSCDigis but discovered simhits access was 'hidden' in SimMuon/MCTruth/PSimHitMap. The MCTruth package has a lot of code which has not been adapted to the consumes interface, so I have just copied the PSimHitMap class that MuonCSCDigis needs into MuonCSCDigis and  then adapted it with the consumes interface. MuonCSCDigis still compiles and builds. But not properly tested - I am just trying to keep this package alive for potential future use. On the positive side this removes a dependence on the MCTruth package.