Users should be able to rotate and resize images (uploaded from computer) in builder

[jwirfs-brock]

I know we tackled this one a while back and ran into some technical issues, but I've observed users (many times):

• trying to upload an image from their computer that was taken with a digital camera -- the image will be huge and possibly in the wrong orientation
• they don't know how to resize and rotate it on their desktop before uploading it (or find this to be tedious and frustrating)

Also, this relates to #717. We should probably have maximum image dimensions -- they should never extend beyond the story viewer window (readers shouldn't have to scroll to see the entire image).