0.3.1: Minor renaming bugs

[illustris 3]

1. Typing anything overwrites the name instead of appending

2. 16 character long names bounce up and down when being edited

[Micha 673]

Thanks for reporting, I'll have a look at it

[DreamShark 41]

I prefer it overwriting the existing name, but having the option to append by maybe clicking the name again would be nice (maybe keep undo, Ctrl+Z, active in case someone accidentally overwrites a name they wanted to append) or maybe a Cancel button next to the Pencil icon.