Calculate systematic normalization errors properly when `MONIT` and `MONIT-ERR` fields are supplied

[beykyle]

This means the systematic error in the normalization is (sigma_N/N) * (S) where sigma_N is MONIT-ERR, N is MONIT and S=y/N is the normalized quantity. Therefore, the fractional err in normalization is just MONIT-ERR/MONIT