Fix error during rotation

Fix https://github.com/GNS3/gns3-gui/issues/1474

gns3server/schemas/drawing.py

@@ -50,7 +50,7 @@ DRAWING_OBJECT_SCHEMA = {
         "rotation": {
             "description": "Rotation of the element",
             "type": "integer",
-            "minimum": 0,
+            "minimum": -359,
             "maximum": 360
         },
         "svg": {

gns3server/schemas/label.py

@@ -33,7 +33,9 @@ LABEL_OBJECT_SCHEMA = {
         },
         "rotation": {
             "description": "Rotation of the label",
-            "type": "integer"
+            "type": "integer",
+            "minimum": -359,
+            "maximum": 360
         },
     },
     "required": [