[IMPLEMENTED] Permission for posting to newsfeed


We would like the ability to restrict posting to the newsfeed to only certain group roles, so regular group members can't post to it. Currently, there are only options for role permissions on being able to edit/delete own or any newsfeed comments in "Manage comments", no permission option to post newsfeed comments in the first place.

As a bonus, it would be nice to have another permission which would allow people to reply/comment on existing newsfeed comments, but not post new ones, but this is a secondary lesser request.