Process some options on the server, in addition to the client

[bdukes]

When marking the Random Order option, this should randomize on the server, as well as the client. The client only starts randomizing after the first rotation (and obviously doesn't do anything with the order before it's initialized).

Also, when marking the rotator to auto-stop after a certain number of slides, if that number is fewer than the number of slides altogether, trim the collection on the server, so you don't send down slides that aren't used.