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.
Merge pull request #450 from bjarnef/7.1.5

Fix for U4-5313 and U4-5330