Author and editors group checking while viewing a draft

[ivanvenosdel]

This is an enhancement to the feature that allows a user to view an unpublished entry on their site when they are logged in as the author of the entry. The entry displays a 'draft' badge when they are viewing it.

We should add a feature that also makes it viewable to those in an "editors group". The name of the group that is checked against would be configurable and would default to "andablog-editors". With this functionality either the author OR anyone in the configured group could view the draft.