(1) Chapters 401 to 411 must be liberally construed and applied to promote its underlying purposes and policies, which are all of the following:
(a) To simplify, clarify, and modernize the law governing commercial transactions.
(b) To permit the continued expansion of commercial practices through custom, usage, and agreement of the parties.
(c) To make uniform the law among the various jurisdictions.
(2) Unless displaced by the particular provisions of chs. 401 to 411, the principles of law and equity, including the law merchant and the law relative to capacity to contract, principal and agent, estoppel, fraud, misrepresentation, duress, coercion, mistake, bankruptcy, or other validating or invalidating cause shall supplement its provisions.