* First steps splitting out the Amortization and Deprecation Excel functions from Financials
* Verify which methods allow negative values for arguments
* Additional unit tests for SLN() and SYD()
* Additional unit tests for DDB()
* Additional unit tests for DB()
* Verify Amortization cases where salvage is greater than cost
* More unit tests for Amortization
* Resolve broken test in AMORLINC() and extract amortizationCoefficient calculation
* verify amortizationCoefficient calculation
* Extract YIELDDISC() and YIELDMAT() to Financial\Securities
* Additional validation for Securities Yield functions