Dockerfile argument to set container user UID

The UID of created user should be set to the UID of the user that will
be running the image/container to set appropriate permissions on files
within notebooks directory. Default 1000 should be ok for users using
the default account created while installing linux.

docker/docker-compose.yml

@@ -6,6 +6,7 @@ services:
       dockerfile: ./docker/Dockerfile
       args:
         - username=devel
+        - userid=1000
     container_name: handson-ml
     image: handson-ml
     logging: