Change node_id when I save as

Fix https://github.com/GNS3/gns3-gui/issues/1519

gns3server/controller/import_project.py

@@ -111,6 +111,26 @@ def import_project(controller, project_id, stream, location=None, name=None, kee
 
                 yield from _move_files_to_compute(compute, project_id, path, os.path.join("project-files", node["node_type"], node["node_id"]))
 
+        # Generate a new node id
+        node_old_to_new = {}
+        for node in topology["topology"]["nodes"]:
+            if "node_id" in node:
+                node_old_to_new[node["node_id"]] = str(uuid.uuid4())
+                _move_node_file(path, node["node_id"], node_old_to_new[node["node_id"]])
+                node["node_id"] = node_old_to_new[node["node_id"]]
+            else:
+                node["node_id"] = str(uuid.uuid4())
+
+        # Update link to use new id
+        for link in topology["topology"]["links"]:
+            link["link_id"] = str(uuid.uuid4())
+            for node in link["nodes"]:
+                node["node_id"] = node_old_to_new[node["node_id"]]
+
+        # Generate new drawings id
+        for drawing in topology["topology"]["drawings"]:
+            drawing["drawing_id"] = str(uuid.uuid4())
+
         # And we dump the updated.gns3
         dot_gns3_path = os.path.join(path, project_name + ".gns3")
         # We change the project_id to avoid erasing the project
@@ -126,6 +146,24 @@ def import_project(controller, project_id, stream, location=None, name=None, kee
     return project
 
 
+def _move_node_file(path, old_id, new_id):
+    """
+    Move the files from a node when changing his id
+
+    :param path: Path of the project
+    :param old_id: ID before change
+    :param new_id: New node UUID
+    """
+    root = os.path.join(path, "project-files")
+    if os.path.exists(root):
+        for dirname in os.listdir(root):
+            module_dir = os.path.join(root, dirname)
+            if os.path.isdir(module_dir):
+                node_dir = os.path.join(module_dir, old_id)
+                if os.path.exists(node_dir):
+                    shutil.move(node_dir, os.path.join(module_dir, new_id))
+
+
 @asyncio.coroutine
 def _move_files_to_compute(compute, project_id, directory, files_path):
     """