- SemanticScuttle_Filter
  -> class with static filter functions to filter
     ids, usernames, passwords, sorting etc.
- find out the reasoning behind define(POST_|GET_)
- when a user gets deleted from database, he should not be
  logged in anymore (name not shown on top right)
- Make users inactive by default when registered newly
  - have to be activated by admins
- Deactivate user registration
- Hide bookmarks with vote < 0 (or threshold) from unregistered users