self-adjusting layout when making issue editor wider or higher (BB-2093)

Hi,

The issue editor can be made wider and higher using the handle in the lower right corner. Which I think is a great feature. But I experienced some layout imperfections doing this.

1. It would be nice if the width of the preview would also be automatically adjusted to that of the editor.
2. It would be nice if the height of the preview would also be automatically adjusted to that of the editor.
3. It would be nice if the editor was lowered a bit, when making it
   wider, so the administration fields stay completely in view.

I attached a screenshot making things clear visually.

The same remark/request is valid for when adding a comment. And when adding a comment the handy blue border around the editor is missing too .

Greets,
Johan