Support graph read mode for olap property

[zhoney]

Expected behavior 期望表现

{type something here...}

Actual behavior 实际表现

{type something here...}

Steps to reproduce the problem 复现步骤

1. {step 1}
2. {step 2}
3. {step 3}

Status of loaded data 数据状态

Vertex/Edge summary 数据量

• loaded vertices amount: {like 10 million}
• loaded edges amount: {like 20 million}
• loaded time: {like 200s}

Vertex/Edge example 数据示例

{type something here...}

Schema(VertexLabel, EdgeLabel, IndexLabel) 元数据结构

{type something here...}

Specifications of environment 环境信息

• hugegraph version: {like v0.7.4}
• operating system: {like centos 7.4, 32 CPUs, 64G RAM}
• hugegraph backend: {like cassandra 3.10, cluster with 20 nodes, 3 x 1TB HDD disk each node}

[zhoney]

already implemented in #1332

[ivanReckless]

How did you make it? I really need your help with this fxxking "graph_read_mode" shit. I really could not follow the "PUT" method in the DOCUMENT. Tried many times, but code 400 always. If you have the time, please! Thank you!