Improve user homepage

Improve user homepage

1) Only consider user's with 'status': 'active'. We don't want to
   display unconfirmed/blocked users, right?
2) Actually query user's media in the view and display on their home
   page.
3) Throw an error 404 if we don't find a valid user, rather than saying,
   "User not found" (from within the template).
4) Pass in medias as media_entries to remain compatible with the 'root'
   page.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>