Rename dialog: Patch for review

[Kevin Connor Arpe <kevinarpe gmail com>]

Hello,

There are a few small changes I would to make for the rename dialog.
Example: Fix tiny layout / margin issues and auto-size new name
GtkEntry (if current sheet name is very long).

I git-clone'd your repo and made changes (locally) to master branch.
I've tested the changes locally on my PC.  Now is the time to get some
feedback & review.

This is my first time to submit a patch for this project.  What is the
procedure?

Thanks,
Arpe
Hongkong