Add utility function for First Cost Factoring tool in python

[colleenskemp]

Need: Implement First Cost Factoring tool into python

To find First Cost Factoring table and formulas: Find First Cost Factoring in First Cost tab.

See example in BiomassPower_RRS_ELECGEN_26June2020, First cost tab, A91

Acceptance criteria: Utility function that will do the First Cost factoring calculations.