[SPARK-4077][SQL] Spark SQL return wrong values for valid string timestamp values

In org.apache.hadoop.hive.serde2.io.TimestampWritable.set , if the next entry is null then current time stamp object is being reset.
However because of this hiveinspectors:unwrap cannot use the same timestamp object without creating a copy.

Author: Venkata Ramana G <ramana.gollamudihuawei.com>

Author: Venkata Ramana Gollamudi <ramana.gollamudi@huawei.com>

Closes #3019 from gvramana/spark_4077 and squashes the following commits:

32d818f [Venkata Ramana Gollamudi] fixed check style
fa01e71 [Venkata Ramana Gollamudi] cloned timestamp object as org.apache.hadoop.hive.serde2.io.TimestampWritable.set will reset current time object
[SPARK-4154][SQL] Query does not work if it has "not between " in Spark SQL and HQL

if the query contains "not between" does not work like.
SELECT * FROM src where key not between 10 and 20'

Author: ravipesala <ravindra.pesala@huawei.com>

Closes #3017 from ravipesala/SPARK-4154 and squashes the following commits:

65fc89e [ravipesala] Handled admin comments
32e6d42 [ravipesala] 'not between' is not working
[SPARK-2220][SQL] Fixes remaining Hive commands

This PR adds support for the `ADD FILE` Hive command, and removes `ShellCommand` and `SourceCommand`. The reason is described in [this SPARK-2220 comment](https://issues.apache.org/jira/browse/SPARK-2220?focusedCommentId=14191841&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14191841).

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #3038 from liancheng/hive-commands and squashes the following commits:

6db61e0 [Cheng Lian] Fixes remaining Hive commands
[SPARK-4141] Hide Accumulators column on stage page when no accumulators exist

WebUI

Author: Mark Mims <mark.mims@canonical.com>

This patch had conflicts when merged, resolved by
Committer: Josh Rosen <joshrosen@databricks.com>

Closes #3031 from mmm/remove-accumulators-col and squashes the following commits:

6141cb3 [Mark Mims] reformat to satisfy scalastyle linelength.  build failed from jenkins https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/22604/
390893b [Mark Mims] cleanup
c28c449 [Mark Mims] looking much better now... minimal explicit formatting.  Now, see if any sort keys make sense
fb72156 [Mark Mims] mimic hasInput.  The basics work here, but wanna clean this up with maybeAccumulators for column content
[SPARK-4150][PySpark] return self in rdd.setName

Then we can do `rdd.setName('abc').cache().count()`.

Author: Xiangrui Meng <meng@databricks.com>

Closes #3011 from mengxr/rdd-setname and squashes the following commits:

10d0d60 [Xiangrui Meng] update test
4ac3bbd [Xiangrui Meng] return self in rdd.setName