On-Demand loading and some of its side-effects

Hello,

we have implemented an on-demand loading scheme for thumbnails, which loads thumbnails visible in the thumbnails-list and one page ahead and back (in case the user intiially clicks on the to-the-left-button). Details are written in the README.


There was one issue with the lazy thumbnails occupying space before being ready (5ed3ca8) that had to be resolved for this to work properly.

I have only tested the 'ondemand'-feature with the classic theme, it should probably be marked as experimental in the documentation. However, for large image collections, it should reduce downloads from the server.