Add entity moderation status to table

@EthanT, the addition of entity's moderation status in entity browser table is super timely. thank you!
This is a good opportunity to expose default entity status when moderation is not enabled for a specific entity type. E.g. "Published / unpublished" instead of "Not moderated".

I also recommend keeping CSS rules for `.moderation-status` selector out of this patch. Projects can target this selector within their custom themes.

@EthanT I have edited you patch slightly to use dependency injection and made the new function names a bit more explicit.
Please could you review and let me know.

Thanks again for all your contributions.

Cool. Merged into the dev branch.
New release coming soon.

The merge left the field widget broken, as the method getStatusColumnHeader() is missing in the current dev version.

Edit: It's not been the merge itself, but the renaming of commit c8b1b6c1da86ae6d9128bab6f115af63b18940b7. There is still a reference to the old name left in line 187.

The attached patch fixes the error. (Didn't open another issue for the sake of a fast fix.)