Consolidate central system units into a single performance map for both single- and multi-pass operation.

[nealkruis]

It seems like the ranges of evaporator and inlet temperatures are the same. The difference is only the flow rate / delta temperature range, but if we have an adequate range to cover single-pass operation (e.g., delta T from 0-90F), the same map should be able to be used for multi-pass operation (e.g. delta T = 10F). The multi-pass variants will just fix the flow rate for simulation