Added SystemCost Expression to standardize cost evaluation and reconstruction, esp with Pyomo 4.2
Added SystemCost Expression to standardize cost evaluation and reconstruction, esp with Pyomo 4.2

bmaluenda/SWITCH-Pyomo-Chile,bmaluenda/switch,bmaluenda/SWITCH-Pyomo-Chile,OCM-Lab-PUC/switch-chile,OCM-Lab-PUC/switch-chile