Syncthing Gtk3-based graphical interface

Graphical user interface with notification area icon for Syncthing based on Gtk3 and Python.

Supported Syncthing features:
 * Everything what WebUI can display.
 * Adding / editing / deleting nodes.
 * Adding / editing / deleting repositories.
 * Restart / shutdown server.
 * Editing daemon settings.

Additional features:
 * First run wizard for initial configuration.
 * Running Syncthing daemon in background.
 * Half-automatic setup for new nodes and repositories.
 * Filesystem watching and instant synchronization using inotify.
 * Caja, Nautilus, and Nemo file managers integration.
 * Desktop notifications.