Custom Entity AutoPublish: Move logic server side

[HeyJoel]

Currently the auto-publish setting on a custom entity definition is handles client side in the admin panel. I'm pretty sure there was a good reason for doing it this way at the time, but the backend commands don't work as expected e.g. if I use AddCustomEntityCommand for an auto-publish entity, I have to remember to set Publish = true.

It's also worth looking into how auto-publish works with the visual editor, as one reason this may have been done client side would be to prevent many versions from being created as you add blocks to a page.