## 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.
e3f8a03367