Code quality and code coverage guards are coming

[Xiangdong Huang <sa...@gmail.com>]

Hi all,

I open a PR to enable sonar code quality check and code coverage check[1].

You can get current code quality report on [2].

As for the code coverage, currently I have to set the check threshold as 0
(for method coverage, class coverage, and branch coverage).

And, I suggest that we can hold a online hackathon every month, called
Pac-Man or Chicken Run. That is, every month, let's increase the threshold
of the code coverage. For example, it is 0% in Jan, and 5% in Feb, 10% in
Mar, etc..
If we can not increase the code coverage on that month, all test will
fail..

[1] https://github.com/apache/incubator-iotdb/pull/645/
[2] https://sonarcloud.io/dashboard?id=apache_incubator-iotdb
Best,
-----------------------------------
Xiangdong Huang
School of Software, Tsinghua University

 黄向东
清华大学 软件学院