Make Imagecache optional

Hi there,

I've been trying out jquery_slideshow and really like it, except for the fact that it requires an imagecache preset. I'm working on a site which will be quite image-heavy. The images that will be uploaded for the slideshow will already have the correct width/height, I needed to create an imagecache preset with no configured actions just to get jquery_slideshow to work, which is a shame IMHO. It's extra work to configure that (and it's not very intuitive that that is neccessary) and also doubles all storage requirements, which means a lot of extra megabytes will be wasted as the dummy imagecache preset will just make a copy of the original image.

Here's a patch that adds a new formatter option to just use the imagefield directly, with no imagecache preset. I hope you will consider adding this, as it would make jquery_slideshow a little more lightweight and easier to use out-of-the-box (no requirement to configure an imagecache preset). I haven't tested it (since I am using imagecache elsewhere), but it should even work now on sites where imagecache is not installed at all.

The width and height checks don't seem necessary (the code works without them). Perhaps they can be removed for all cases?