Liquidation Waterfall Module

[iamdefinitelyahuman]

Liquidation Waterfall Module

Requirements before merging:

• unit tests
• comparison of results with confirmed-accurate real-world waterfall calculations
• documentation
• clean up or remove waterfall.py (python mockup that was used for developing the waterfall logic)

General notes:

• This contract only performs the waterfall calculations, it does not handle the actual distribution of funds. There should be an eventual integration with an escrow contract but that is outside the scope of this PR.