add big white icons for lightbox, slideshow etc

White icons for lightbox, previews, pictures slideshow etc.

As a bonus, finally splitting close and delete button (thought still looking the same for now) _and_ adding on top just for you a darkred hover state to be used for delete, to ensure people are aware of the redness of the situation when they hover the delete button and are about to deletify a file.

Sounds good? Vote yes you like nice icons @icewind1991 @Raydiation