Parameterize contingency

[softwareengineerprogrammer]

Description

Parameterizes contingency cost per NREL#383 as:

Contingency Percentage: "The contingency percentage applied to the direct capital costs for stimulation, field gathering system, exploration, and surface plant. (Note: well drilling and completion costs do not have contingency applied and are not affected by this parameter.)"

Testing & Verification

1. Existing behavior unchanged - relevant unit tests pass without changes
2. Added contingency unit test. Validates that varying contingencies from 5-30% have expected effect on capex/cost categories for EGS, absorption chiller, and heat pump.
3. Web interface