Section 8. The principles of law and equity, including the law of corporations and unincorporated associations, the law of real property and the law relative to capacity to contract, principal and agent, eminent domain, estoppel, fraud, misrepresentation, duress, coercion, mistake, receivership, substantial performance, or other validating or invalidating cause shall supplement the provisions of this chapter, except to the extent such principles are inconsistent with this chapter.