Make Bulk Renamer buttons easier to understand

This removes the [Done] (Apply and Close) button from Bulk Renamer, leaving [Close] and [Rename] (where [Rename] renames and leaves the window open).

It also removes the contextual label change where the [Close] button would be [Cancel] until [Rename] was clicked, after which it would become [Close] (this only applied when launching from Thunar). This seems more consistent and as it looks and functions the same both when launched from Thunar and in standalone mode. A tooltip was added to [Close] to explain proposed changes would be disregarded. Let me know if this is okay or if the contextual button was preferred and I can add it back. Just thought this was a little simpler and easier to understand (for me at least) and reduced some code duplication.

Also, in standalone mode [Done] and [Apply] both functioned exactly the same, so I guess this fixes that issue too.

Closes #1032 (closed)

Let me know if there are any changes I need to make. Thanks!