Download covers improvements

There are several inconviniences in this dialog:

1. After you changes in options the search server (amazon.com -> amazon.de for example), it always asks to confirm this change case all images will be lost. Even if there were no images found :). Really annoying.

2. Why do not allow to search all available sites for images? Would be great.

3. Why do not allow to extend search with new sites, like it is done in the Ant Movie Catalog (great program BTW)? I would like to add support of [url]www.rbcmp3.com[/url] - they have almost all russian covers.

That's all for the moment :)

Vlad.