## What changes were proposed in this pull request?
Improve example outputs to better reflect the functionality that is being presented.  This mostly consisted of modifying what was printed at the end of the example, such as calling show() with truncate=False, but sometimes required minor tweaks in the example data to get relevant output.  Explicitly set parameters when they are used as part of the example.  Fixed Java examples that failed to run because of using old-style MLlib Vectors or problem with schema.  Synced examples between different APIs.

## How was this patch tested?
Ran each example for Scala, Python, and Java and made sure output was legible on a terminal of width 100.

Author: Bryan Cutler <cutlerb@gmail.com>

Closes #14308 from BryanCutler/ml-examples-improve-output-SPARK-16260.

## What changes were proposed in this pull request?

Cleanup of examples, mostly from PySpark-ML to fix minor issues:  unused imports, style consistency, pipeline_example is a duplicate, use future print funciton, and a spelling error.

* The "Pipeline Example" is duplicated by "Simple Text Classification Pipeline" in Scala, Python, and Java.

* "Estimator Transformer Param Example" is duplicated by "Simple Params Example" in Scala, Python and Java

* Synced random_forest_classifier_example.py with Scala by adding IndexToString label converted

* Synced train_validation_split.py (in Scala ModelSelectionViaTrainValidationExample) by adjusting data split, adding grid for intercept.

* RegexTokenizer was doing nothing in tokenizer_example.py and JavaTokenizerExample.java, synced with Scala version

## How was this patch tested?
local tests and run modified examples

Author: Bryan Cutler <cutlerb@gmail.com>

Closes #14081 from BryanCutler/examples-cleanup-SPARK-16403.

[SPARK-15134][EXAMPLE] Indent SparkSession builder patterns and update binary_classification_metrics_example.py

## What changes were proposed in this pull request?

This issue addresses the comments in SPARK-15031 and also fix java-linter errors.
- Use multiline format in SparkSession builder patterns.
- Update `binary_classification_metrics_example.py` to use `SparkSession`.
- Fix Java Linter errors (in SPARK-13745, SPARK-15031, and so far)

## How was this patch tested?

After passing the Jenkins tests and run `dev/lint-java` manually.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12911 from dongjoon-hyun/SPARK-15134.

## 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.

## What changes were proposed in this pull request?

This pull request adds a python example for train validation split.

## How was this patch tested?

This was style tested through lint-python, generally tested with ./dev/run-tests, and run in notebook and shell environments. It was viewed in docs locally with jekyll serve.

This contribution is my original work and I license it to Spark under its open source license.

Author: JeremyNixon <jnixon2@gmail.com>

Closes #11547 from JeremyNixon/tvs_example.