Add progress bar to bug report submission

I've seen many mentions of how long it takes to submit a bug report, especially for large maps. In my case I left it running for over ten hours, and still had not submitted the bug report on a 50x50 map. A progress bar would make you clear if something is actually happening, or if the submission is just stuck and is never going to finish. It would also be good to prevent people from canceling the submission just before it finishes…