Implement basic sync functionality

[tamasstephen]

• find a way to synchronize user boards
• test the ways with basic functionality e.g. logging
• implement basic sync.:
  • If a new board was created it appears on the side of the other users
  • The basic sync does not handles single boards e.g. does not render just a single board:
    • The basic sync re-renders the whole board (with AJAX) if all boards are closed
  • The basic sync does nothing if one of the boards is open