Hotfix/test

updates for Java Connector

[add Integrating network connectivity test into Taos program]

fix timestamp precision description.

udpate tests cases for defects

natural interval

Merge from develop into Master

improve the readme document with building steps

Feature/os

remove gitee relative part.

[modify oem macro define]

Update faq-ch.md

improve building steps with specific linux distributions

Fixed a problem with crash_gen tool, so that it releases DB connections properly

Fmaster/lihui

add test cases