Entity status + drafty

Same changes as https://www.drupal.org/node/2389185
I think I'd personally go for adding that to the selector form as an extra option, then removing it from the database - makes it extra clear.

I also noticed when writing the patch that we'd often be loading the published changeset from the database when validating changesets etc., whereas we know that the published changeset is always valid and could therefore skip the entity_load() in those cases.