Batch Feature Doesn't Do Anything

This was bugging me, so I patched it here:

https://gist.github.com/krues8dr/b5aae1a324bf15513eeddc9f7ab91cbe

There were a few things that were broken:?they were using numberposts instead of posts_per_page; the second block of the batch/offset check wasn’t limiting to $batch posts, the counting wasn’t being done properly for the post types, and the whole admin page was showing for the Continue option, instead of just the continue form.