add server python API

seperate client and server: we may support multiple version of client, but server can be only one version

make general_model_config unified on client side and server side
make general_model_config accessible with Python API

add  c++ code for general server

merge upstream/develop

add cube press doc && general client batch predict

fix compile bug : fix general-client CMakeLists.txt &&  rm useless file in cube folder

Add save api