[*] FO : Wait for the image to be loaded before displaying the big image on product page

First commit:
On the product page when hovering the thumbnails, the image fade in was called immediately without being checking if the image was loaded. This could cause some flash with the old image.

Ps: my text editor is configured to trim trailing white spaces and I realized after it modified others lines other than the one with the code I changed. The edit I made is line 439 to 443.

Second commit:
I've seen this `@todo` comment forever, so I made it.