[SPARK-15031][EXAMPLE] Use SparkSession in Scala/Python/Java example.

## What changes were proposed in this pull request?

This PR aims to update Scala/Python/Java examples by replacing `SQLContext` with newly added `SparkSession`.

- Use **SparkSession Builder Pattern** in 154(Scala 55, Java 52, Python 47) files.
- Add `getConf` in Python SparkContext class: `python/pyspark/context.py`
- Replace **SQLContext Singleton Pattern** with **SparkSession Singleton Pattern**:
  - `SqlNetworkWordCount.scala`
  - `JavaSqlNetworkWordCount.java`
  - `sql_network_wordcount.py`

Now, `SQLContexts` are used only in R examples and the following two Python examples. The python examples are untouched in this PR since it already fails some unknown issue.
- `simple_params_example.py`
- `aft_survival_regression.py`

## How was this patch tested?

Manual.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12809 from dongjoon-hyun/SPARK-15031.

1 files changed, 5 insertions, 0 deletions

diff --git a/python/pyspark/context.py b/python/pyspark/context.py
index cb15b4b91f..aec0215b40 100644
--- a/python/pyspark/context.py
+++ b/python/pyspark/context.py
@@ -952,6 +952,11 @@ class SparkContext(object):
         """
         self.profiler_collector.dump_profiles(path)
 
+    def getConf(self):
+        conf = SparkConf()
+        conf.setAll(self._conf.getAll())
+        return conf
+
 
 def _test():
     import atexit