Remove dead code to do with `Editor.editMode`.

[zuckerruebe]

editMode is only ever 1. At some point, it seems to have taken on other values. There are still pieces of code lying around that check the value of editMode and do different things depending on its value. As a developer, I'd like editMode and those branches that depend on values of editMode being different from 1 to be removed in order to have less dead code lying around.