Bump document version

Author: mmwinther

src/datadoc/datadoc-json-schema.json

@@ -10,7 +10,7 @@
     },
     "document_version": {
       "description": "Version of this model",
-      "const": "5.0.1"
+      "const": "6.0.0"
     },
     "dataset": {
       "type": "object",