Prioritize functions from base

[matt-noonan]

Given two equally-ranked matches, one in base and one in some other package, we should prefer the base match. This should be simple, we just need to add a small penalty for non-base matches (or some other rule that has the same effect)

[ndmitchell]

Note that the Id values are ordered via a priority system, so given two equal matches, the one with Id lower is higher priority. As you might expect, base comes first, but common libraries with lots of dependencies also go lower too.