Fixes T5424.
- One concrete issue: drafts were not being cleared properly because __draft__ was not set on submission. This (mostly) fixes phantom drafts.
- This ajax comment magic feels weird and floaty and generally has problems. For example, if you add subscribers or inlines, all the stuff on the page which represents those won't update automatically. Instead, just reload. Maybe we'll ajax this stuff some day, but it feels like a net negative for now.
- Also remove it from other applications where it's currently used.
- Fix an issue with inline previews.