* Extract remaining Financial function unit tests into separate test classes for each function
This makes it easier to manage unit tests if they are individual files rather than all in a single file
It also provides a stepping stone toward making it easier to test Excel functions when Excel errors no longer return a string, but an actual Excel exception that can be handled more cleanly
* Additional unit tests for previously untested financial functions, and some additions to follow untested paths
* Start splitting Financial function tests out from the large FinancialTests class into individual test classes for each function