Note: this currently needs to remove a warning from load_concepts.itm, which may not be desired. Maybe there is another way to prevent unnecessary warnings in the case of additional arguments to load_concepts?

load_mihi, load_au, and load_ei only differ in the rounding function they apply (and the fact that eicu strictly speaking doesn't require merging of origin). They can thus all be replaced with a single function that receives the rounding function as a parameter.