MDIO-Python v1.0 alignment for fill values #161
Description
Some changes should be implemented to better align with how mdio-python will be implemented. Historically, MDIO files are written with 0 or 0.0 fill values. mdio-cpp uses null and NaN currently.
To better align with the MDIO-python standards, we must update the fill values. This task should use the values that are defined by the Python implementation.