Replace snapshots by import / export

Fix #1042

gns3server/handlers/api/controller/__init__.py

@@ -22,4 +22,5 @@ from .link_handler import LinkHandler
 from .server_handler import ServerHandler
 from .drawing_handler import DrawingHandler
 from .symbol_handler import SymbolHandler
+from .snapshot_handler import SnapshotHandler
 from .gns3_vm_handler import GNS3VMHandler