Updates of IoTDB Group By Fill Query

Hi! I'm working on Group By Fill Query these days, to enrich the capabilities of group by fill. Formerly, group by fill only support last_value aggregation using PreviousFill. But now group by fill supports all aggregation functions and fill methods! I modified the fill syntax and

reply for issue IOTDB-973

Hi Yanhong, Thank you for reminding me with this bug. I've fixed it. Thanks, --- Rongzhao Chen School of Software, Tsinghua University ---- ??:

I've submitted a PR for issue IOTDB-972

Hi, I've submitted a PR for issue IOTDB-972 [https://github.com/apache/iotdb/pull/1906]. I used code that .sh couldn't recognize. Now I change the start-cli.sh file into sh version Thanks, --- Rongzhao Chen School of Software, Tsinghua University

I've submitted a PR for issue IOTDB-931

I've submitted a PR for issue IOTDB-931[https://issues.apache.org/jira/browse/IOTDB-931]