define this for all models,
currently only discrete, MLE models that use an optimizer, define mle_settings
rename mle_settings -> fit_settings
add method="lsq" or method="irls"` to linear models, genmod and robust.
for GLSAR and GLSHet, method="ilsq" iterated least squares
plus add some information to fit_settings about the fit details for robust, genmod
or use whatever full names in method that we want to use in summary.