MBS-8212: Edit data sent by the release editor should exclude unchanged fields

This addresses the general problem of the release editor sending unchanged data along with the request, so that it doesn't override other edits entered in the meantime. I guess it's not an incredibly common occurrence if there weren't more tickets about it sooner, but still wrong and annoying. :/

The main change was just adding a removeEqual function similar to the one Edit::WithDifferences uses on the server. It accepts a list of fields to always include, used for entity ids here.