Be able to filter Activity Stream from the UI

Let the users filter from the UI what the Activity Stream shows:

• All
• Author filters - events launched by a certain user
  • only changes done by me; (covered somehow by the Profile AS)
  • specific user;
  • specific group;
• Level filters - events launched at a specific level
  • only changes for a specific page; (covered somehow by the history)
  • only changes for the current space;
  • only changes for the current wiki;
• Type filters
  • entities:
    • pages - display just events launched on pages
    • applications
    • users (user creation, profile changes, etc.)
    • message stream entries (statuses)
  • objects:
    • just annotations events
    • just comments events
    • just attachments
• Action filters
  • edit (rename, etc)
  • add
  • delete
  • etc.