nlust, I've drawn your name again on the Registry review list. This one is almost purely refactoring - one commit cleans up some edge cases, too. Please review commit-by-commit and look at the comments to see what's worth looking at closely and what isn't; the bigger changes in terms of line numbers are mostly just moving code around without changing it.
All changes are in daf_butler.
The motivation for some of these changes may not be apparent just looking at the diffs. Basically, it's updating an early version of these Registry helper classes to be more consistent with a much more complete system of Registry helper classes described on this confluence page. I don't think that's required reading for the review, but it may be useful if you're curious why I felt something was worth changing.