Fix for U4-5313 and U4-5330

Make the bottom bar overlap the image cropper focal point and display
the scrollbar if there is overflow. I know the buttons are located a bit
(10px) closer to the top, but you can see the horizontal scrollbar then,
when there is one in e.g. a package. E.g. depending on the screen
resolution, I would in Matrix Property Editor (There is no spoon) prefer
the Umbracos editing section to scroll than add scroll inside the
property editor wrapper, because it give more editing space.