Smarter handling of opening your changes in your current or a split pane

[jonathanlab]

There's a few options regarding choosing in which pane to open the diff view when you click on it in the changes list.

1. Base it off the screen width/DPI: If the user has a big screen, we can split the chat 50/50 with the diff view. If on a smaller screen, don't split, but open it the same pane.
2. Base it off the users last active pane
3. It's important that we let the user configure this behavior because it is a subjective First of all, what's described here should be behavior that's configurable through settings.