[SPARK-4120][SQL] Join of multiple tables with syntax like SELECT .. FROM T1,T2,T3.. does not work in SparkSQL

Right now it works for only 2 tables like below query.
sql("SELECT * FROM records1 as a,records2 as b where a.key=b.key ")

But it does not work for more than 2 tables like below query
sql("SELECT * FROM records1 as a,records2 as b,records3 as c where a.key=b.key and a.key=c.key").

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

Closes #2987 from ravipesala/multijoin and squashes the following commits:

429b005 [ravipesala] Support multiple joins
[SPARK-3968][SQL] Use parquet-mr filter2 api

The parquet-mr project has introduced a new filter api  (https://github.com/apache/incubator-parquet-mr/pull/4), along with several fixes . It can also eliminate entire RowGroups depending on certain statistics like min/max
We can leverage that to further improve performance of queries with filters.
Also filter2 api introduces ability to create custom filters. We can create a custom filter for the optimized In clause (InSet) , so that elimination happens in the ParquetRecordReader itself

Author: Yash Datta <Yash.Datta@guavus.com>

Closes #2841 from saucam/master and squashes the following commits:

8282ba0 [Yash Datta] SPARK-3968: fix scala code style and add some more tests for filtering on optional columns
515df1c [Yash Datta] SPARK-3968: Add a test case for filter pushdown on optional column
5f4530e [Yash Datta] SPARK-3968: Fix scala code style
f304667 [Yash Datta] SPARK-3968: Using task metadata strategy for row group filtering
ec53e92 [Yash Datta] SPARK-3968: No push down should result in case we are unable to create a record filter
48163c3 [Yash Datta] SPARK-3968: Code cleanup
cc7b596 [Yash Datta] SPARK-3968: 1. Fix RowGroupFiltering not working             2. Use the serialization/deserialization from Parquet library for filter pushdown
caed851 [Yash Datta] Revert "SPARK-3968: Not pushing the filters in case of OPTIONAL columns" since filtering on optional columns is now supported in filter2 api
49703c9 [Yash Datta] SPARK-3968: Not pushing the filters in case of OPTIONAL columns
9d09741 [Yash Datta] SPARK-3968: Change parquet filter pushdown to use filter2 api of parquet-mr
Revert "SPARK-1209 [CORE] SparkHadoop{MapRed,MapReduce}Util should not use package org.apache.hadoop"

This reverts commit 68cb69daf3022e973422e496ccf827ca3806ff30.
HOTFIX: Clean up build in network module.

This is currently breaking the package build for some people (including me).

This patch does some general clean-up which also fixes the current issue.
- Uses consistent artifact naming
- Adds sbt support for this module
- Changes tests to use scalatest (fixes the original issue[1])

One thing to note, it turns out that scalatest when invoked in the
Maven build doesn't succesfully detect JUnit Java tests. This is
a long standing issue, I noticed it applies to all of our current
test suites as well. I've created SPARK-4159 to fix this.

[1] The original issue is that we need to allocate extra memory
for the tests, happens by default in our scalatest configuration.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #3025 from pwendell/hotfix and squashes the following commits:

faa9053 [Patrick Wendell] HOTFIX: Clean up build in network module.