FASTBUILD WIP: avoid NPE on fake login
Handle renames from outside conceptdiagram plugin

Slightly overhaul the way we frame the label rename
logic: it's not the current label overwriting the
previous one; it's more committing a provisional
label over the current one.

The plugin reflects the provisional label (something
you may be typing in but haven't hit enter on yet)
WIP: renames are still awkward