Allow options for lightbox

[d2a-raudenaerde]

I try to integrate the lightbox2 into my application, but I want to tweak how the lightbox behaves (for example, I'd like in centered in the screen). The js-lightbox library exposes a lot of options, which are not avaibable in Wicket in java. I would be nice to be able to set them

[martin-g]

Please send a Pull Request!