#284 Change C++ SDK to shread library

- \#204 - improve grpc performance in search

- \#207 - Add more unittest for config set/get

- \#208 - optimize unittest to support run single test more easily

- \#284 - Change C++ SDK to shread library

## Task

// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License.  You may obtain a copy of the License at

//

//   http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied.  See the License for the

// specific language governing permissions and limitations

// under the License.

#define MILVUS_VERSION "0.6.0"

#define BUILD_TYPE "Debug"

#define BUILD_TIME "2019-11-12 10:25.02"

aux_source_directory(interface interface_files)

aux_source_directory(grpc grpc_client_files)

add_library(milvus_sdk STATIC

add_library(milvus_sdk SHARED

        ${interface_files}

        ${grpc_client_files}

        ${grpc_service_files}