Made RollingWindow exceptions more verbose
Made RollingWindow exceptions more verbose

This should help users better understand the source of their RollingWindow errors.

AlexCatarino/Lean,QuantConnect/Lean,AlexCatarino/Lean,jameschch/Lean,jameschch/Lean,JKarathiya/Lean,StefanoRaggi/Lean,JKarathiya/Lean,JKarathiya/Lean,QuantConnect/Lean,jameschch/Lean,StefanoRaggi/Lean,QuantConnect/Lean,StefanoRaggi/Lean,JKarathiya/Lean,jameschch/Lean,AlexCatarino/Lean,jameschch/Lean,StefanoRaggi/Lean,AlexCatarino/Lean,QuantConnect/Lean,StefanoRaggi/Lean