Support for receiving notifications from node

Changes:

• Add HTTP server for receiving notifications from node. Each node during startup runs own server in separate thread and connects node to it.
  • Following notifications are handled: http_listening, ws_listening p2p_plugin_started, synchronization_started, live_mode_entered, replay_finished, snapshot_dumped and all with name error
  • Notifications about errors immediately raises exception in main thread
  • Use notifications about completion of replaying and snapshot loading to wait during node startup, if such actions are executed.
  • Remove all stderr.txt parsing from node. All needed information are received directly from received notifications.
  • Remove temporary workaround for problem with parsing stderr.txt.

Minor changes:

• Add access to supported node plugins with Node.get_supported_plugins
• Fix bug with missing Node.close call in Node.handle_final_cleanup.
• Remove Plugin -- specialized config entry type
• Raise exception when server thread cannot be joined
• Test node restart.