Created by: guru4elephant

add general_get_conf_str op, add get_config_str client api, refine request and response proto to add new workflow

before update

import sys
from paddle_serving_client import Client

client = Client()
client.load_client_config(sys.argv[1])
client.connect(["127.0.0.1:9393"])

after update

from paddle_serving_client import Client

client = Client()
client.connect(["127.0.0.1:9393"])