Implement cursor info tip showing image coordinates under the cursor.

Showing the info div on the top right of the cursor until there is no room on the right. When no room on the right, then the info div shows up on the top left of the cursor.

@larz0 I switch to crosshair cursor for now, but I would like to use a custom one if you can provide one like the one used in Photoshop. I also made the x and y coordinates right aligned as you suggested.

@couzteau I did some cleanup and made the image scale div always showing inside the image rectangle (fixing third bullet point in #5686).