Display progress during first epoch

Since the first epoch takes a long time, and the progress bar is frozen at this time, we should show the user some progress during this.

I think some sort of message that is displayed as each image is processed would be good, if we decide to keep the progress bar as it is.

@benjijamorris we discussed this a while ago, and you mentioned theres a way to look for progress during this first epoch, can you specify here