[SPARK-3011][SQL] _temporary directory should be filtered out by sqlContext.parquetFile

Author: Chia-Yung Su <chiayung@appier.com>

Closes #1924 from joesu/bugfix-spark3011 and squashes the following commits:

c7e44f2 [Chia-Yung Su] match syntax
f8fc32a [Chia-Yung Su] filter out tmp dir
[SPARK-2927][SQL] Add a conf to configure if we always read Binary columns stored in Parquet as String columns

This PR adds a new conf flag `spark.sql.parquet.binaryAsString`. When it is `true`, if there is no parquet metadata file available to provide the schema of the data, we will always treat binary fields stored in parquet as string fields. This conf is used to provide a way to read string fields generated without UTF8 decoration.

JIRA: https://issues.apache.org/jira/browse/SPARK-2927

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1855 from yhuai/parquetBinaryAsString and squashes the following commits:

689ffa9 [Yin Huai] Add missing "=".
80827de [Yin Huai] Unit test.
1765ca4 [Yin Huai] Use .toBoolean.
9d3f199 [Yin Huai] Merge remote-tracking branch 'upstream/master' into parquetBinaryAsString
5d436a1 [Yin Huai] The initial support of adding a conf to treat binary columns stored in Parquet as string columns.
[SQL] Python JsonRDD UTF8 Encoding Fix

Only encode unicode objects to UTF-8, and not strings

Author: Ahir Reddy <ahirreddy@gmail.com>

Closes #1914 from ahirreddy/json-rdd-unicode-fix1 and squashes the following commits:

ca4e9ba [Ahir Reddy] Encoding Fix
[SPARK-2925] [sql]fix spark-sql and start-thriftserver shell bugs when set --driver-java-options

https://issues.apache.org/jira/browse/SPARK-2925

Run cmd like this will get the error
bin/spark-sql --driver-java-options '-Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,address=8788,server=y,suspend=y'

Error: Unrecognized option '-Xnoagent'.
Run with --help for usage help or --verbose for debug output

Author: wangfei <wangfei_hello@126.com>
Author: wangfei <wangfei1@huawei.com>

Closes #1851 from scwf/patch-2 and squashes the following commits:

516554d [wangfei] quote variables to fix this issue
8bd40f2 [wangfei] quote variables to fix this problem
e6d79e3 [wangfei] fix start-thriftserver bug when set driver-java-options
948395d [wangfei] fix spark-sql error when set --driver-java-options
Minor cleanup of metrics.Source

- Added override.
- Marked some variables as private.

Author: Reynold Xin <rxin@apache.org>

Closes #1943 from rxin/metricsSource and squashes the following commits:

fbfa943 [Reynold Xin] Minor cleanup of metrics.Source. - Added override. - Marked some variables as private.