[SPARK-18279][DOC][ML][SPARKR] Add R examples to ML programming guide.

## What changes were proposed in this pull request?
Add R examples to ML programming guide for the following algorithms as POC:
* spark.glm
* spark.survreg
* spark.naiveBayes
* spark.kmeans

The four algorithms were added to SparkR since 2.0.0, more docs for algorithms added during 2.1 release cycle will be addressed in a separate follow-up PR.

## How was this patch tested?
This is the screenshots of generated ML programming guide for ```GeneralizedLinearRegression```:
![image](https://cloud.githubusercontent.com/assets/1962026/20866403/babad856-b9e1-11e6-9984-62747801e8c4.png

)

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16136 from yanboliang/spark-18279.

(cherry picked from commit eb8dd681)
Signed-off-by: Yanbo Liang <ybliang8@gmail.com>

docs/ml-classification-regression.md

@@ -389,6 +389,14 @@ Refer to the [Python API docs](api/python/pyspark.ml.html#pyspark.ml.classificat
 
 {% include_example python/ml/naive_bayes_example.py %}
 </div>
+
+<div data-lang="r" markdown="1">
+
+Refer to the [R API docs](api/R/spark.naiveBayes.html) for more details.
+
+{% include_example naiveBayes r/ml.R %}
+</div>
+
 </div>
 
 
@@ -566,6 +574,13 @@ Refer to the [Python API docs](api/python/pyspark.ml.html#pyspark.ml.regression.
 {% include_example python/ml/generalized_linear_regression_example.py %}
 </div>
 
+<div data-lang="r" markdown="1">
+
+Refer to the [R API docs](api/R/spark.glm.html) for more details.
+
+{% include_example glm r/ml.R %}
+</div>
+
 </div>
 
 
@@ -755,6 +770,13 @@ Refer to the [Python API docs](api/python/pyspark.ml.html#pyspark.ml.regression.
 {% include_example python/ml/aft_survival_regression.py %}
 </div>
 
+<div data-lang="r" markdown="1">
+
+Refer to the [R API docs](api/R/spark.survreg.html) for more details.
+
+{% include_example survreg r/ml.R %}
+</div>
+
 </div>
 
 

docs/ml-clustering.md

@@ -86,6 +86,14 @@ Refer to the [Python API docs](api/python/pyspark.ml.html#pyspark.ml.clustering.
 
 {% include_example python/ml/kmeans_example.py %}
 </div>
+
+<div data-lang="r" markdown="1">
+
+Refer to the [R API docs](api/R/spark.kmeans.html) for more details.
+
+{% include_example kmeans r/ml.R %}
+</div>
+
 </div>
 
 ## Latent Dirichlet allocation (LDA)