Remove dependence on having a defined NpA or NpV2 for measurements

This MR removes the need to have a defined key value pair for NpA and/or NpV2 for actuation measurement MCMC fitting. Changing these values didn't have any effect on the output because it was divided out anyway, but the mere fact of needing to have it defined caused additional complication and confusion (sometimes making it seem there was some circular logic when there should not be). Here I remove this requirement when processing actuation measurement files.

Note that this dependence was already removed for sensing measurements, but it had not been so for the actuation measurements. It could have been an oversight on my part or looking for "simplicity in code" by leveraging other methods, not realizing this could lead to circular logic confusion. I hope this is now more clear