Post list: authors see their own posts

issue #3446
Limit Posts for Authors.

* Ensures that posts listing only shows posts that the current user
  authored, if they only have the Author role.
* Do not transition into the posts.post route if the current user is
  not the author (but has the Author role). This is needed because
  the API server will always return the post (regardless of the current
  user).
Completed post & user list filer by role

closes #3446, closes #3086

- Authors can only ever get to their own posts
- Editors only ever see authors in the user list
Redirect to the first available post for current user.
Merge pull request #3462 from ErisDS/issue-3446

Post list: authors only see their own posts