Console graph handling and UI re-worked:

 * No more instant updates when changing options
 * Graph updates are triggered on state changes or when the user orders
   additional nodes from the server
 * The user can now add and remove nodes which are of interest. The list
   of node Ids is stored in HTML5 localStorage so that updates are easily
   possible.
 * Removing nodes is possible by drawing a rectangle around them
 * Loading the vicinity of a node doesn't happen for all nodes, but
   instead the user chooses nodes that should be expanded or simply
   double-clicks a node, which will load its vicinity.