Arguments to internal calls to meta::metagen or metafor::rma should be specifiable by the user 

Resulting confMeta objects always contain an element "comparison_ci" that contains CIs from comparison methods. As of now these are "fe" (fixed effect MA), "re" (random effects MA), "hk" (Hartung-Knapp), and "hc" (Henmi-Copas). However, many arguments to these internal calls are hardcoded as of now. Maybe these should also be user specifiable?