(WIP) extend UPDATE MODEL query to accept one shot update

[kmaehashi]

Extend UPDATE MODEL to accept training single data via query.
This is handy for testing JubaQL using interactive shell.

UPDATE MODEL test  USING add WITH '{"duration": 0, "protocol_type": "tcp", "service": "http", "flag": "SF", "src_bytes": 181, "dst_bytes": 5450, "land": 0}'