GenScaler changes broke TH{a/c}ScalerEvtHandler

[sawjlab]

In commit e86eb98 I removed IsSLot from the Decode method in GenScaler.C. IsSlot is called instead in the LoadBank methods. This breaks THaScalerEvtHandler and THcScalerEvtHandler. IsSlot needs to be either put back in the Decode method, or the ScalerEvtHandler classes need to modified to make IsSlot calls to find the scaler headers. I prefer the latter.

I plan to modify the ScalerEvtHandler classes to walk through the bank structure and only examine data in UI4 banks.

[sawjlab]

I rewrote THcScalerEvtHandler a while ago to walk through the bank structure and only examine data in UI4 banks. THaScalerEvtHandler may remain broken.