Add hover description for zoom in zoom out

[Mark-Hetherington]

Hi,

I've added a title tag so users get a description when hovering over the zoom buttons.

I'm also looking at adding additional buttons triggering custom events. My use case is to add an "upload new image" button to replace the image in use, and a "remove image" option but I'm sure there are other use cases as well.

Cheers, Mark