renaming fields moves them to the bottom of the form

This looks like a side effect of the fix for #88. It happens only for fields that haven't been reordered (i.e. when there is no defined ui:order) so the fix might be to always include a ui:order by default. Prior to the mentioned change in fact the ui:order was not being set by default but it was being set on rename, whereas now it's not set on rename, only on reorder.

The issue names no file, test, or entry point; trace the rename and reorder handling in the React form builder, comparing the behavior before and after #88. Reproduce a rename with no ui:order and verify that the field keeps its position while explicit reordering still works.

Written by the indexing model from the issue text.