Add try except blocks to make sure necessary columns are in each file

[bradenpecora]

Raise errors if a necessary column isn't in an input file

[bradenpecora]

But don't raise errors if unnecessary files aren't included. storage.csv is a relic; production_existing.csv and, by consequence ccs.csv (should probably be ccs_retrofit.csv) aren't technically required (or maybe just only one of production_x.csv is required?)