Squashed bug in calculation of variable costs. Also broke out variable costs calculation by project, mirroring the pattern in project_build.
Squashed bug in calculation of variable costs. Also broke out variable costs calculation by project, mirroring the pattern in project_build.

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