[SPARK-16294][SQL] Labelling support for the include_example Jekyll plugin

## What changes were proposed in this pull request?

This PR adds labelling support for the `include_example` Jekyll plugin, so that we may split a single source file into multiple line blocks with different labels, and include them in multiple code snippets in the generated HTML page.

## How was this patch tested?

Manually tested.

<img width="923" alt="screenshot at jun 29 19-53-21" src="https://cloud.githubusercontent.com/assets/230655/16451099/66a76db2-3e33-11e6-84fb-63104c2f0688.png">

Author: Cheng Lian <lian@databricks.com>

Closes #13972 from liancheng/include-example-with-labels.

1 files changed, 6 insertions, 35 deletions

diff --git a/docs/sql-programming-guide.md b/docs/sql-programming-guide.md
index 6c6bc8db6a..68419e1331 100644
--- a/docs/sql-programming-guide.md
+++ b/docs/sql-programming-guide.md
@@ -63,52 +63,23 @@ Throughout this document, we will often refer to Scala/Java Datasets of `Row`s a
 <div class="codetabs">
 <div data-lang="scala"  markdown="1">
 
-The entry point into all functionality in Spark is the [`SparkSession`](api/scala/index.html#org.apache.spark.sql.SparkSession) class. To create a basic `SparkSession`, just use `SparkSession.build()`:
-
-{% highlight scala %}
-import org.apache.spark.sql.SparkSession
-
-val spark = SparkSession.build()
-  .master("local")
-  .appName("Word Count")
-  .config("spark.some.config.option", "some-value")
-  .getOrCreate()
-
-// this is used to implicitly convert an RDD to a DataFrame.
-import spark.implicits._
-{% endhighlight %}
+The entry point into all functionality in Spark is the [`SparkSession`](api/scala/index.html#org.apache.spark.sql.SparkSession) class. To create a basic `SparkSession`, just use `SparkSession.builder()`:
 
+{% include_example init_session scala/org/apache/spark/examples/sql/RDDRelation.scala %}
 </div>
 
 <div data-lang="java" markdown="1">
 
-The entry point into all functionality in Spark is the [`SparkSession`](api/java/index.html#org.apache.spark.sql.SparkSession) class. To create a basic `SparkSession`, just use `SparkSession.build()`:
+The entry point into all functionality in Spark is the [`SparkSession`](api/java/index.html#org.apache.spark.sql.SparkSession) class. To create a basic `SparkSession`, just use `SparkSession.builder()`:
 
-{% highlight java %}
-import org.apache.spark.sql.SparkSession
-
-SparkSession spark = SparkSession.build()
-  .master("local")
-  .appName("Word Count")
-  .config("spark.some.config.option", "some-value")
-  .getOrCreate();
-{% endhighlight %}
+{% include_example init_session java/org/apache/spark/examples/sql/JavaSparkSQL.java %}
 </div>
 
 <div data-lang="python"  markdown="1">
 
-The entry point into all functionality in Spark is the [`SparkSession`](api/python/pyspark.sql.html#pyspark.sql.SparkSession) class. To create a basic `SparkSession`, just use `SparkSession.build`:
-
-{% highlight python %}
-from pyspark.sql import SparkSession
-
-spark = SparkSession.build \
-  .master("local") \
-  .appName("Word Count") \
-  .config("spark.some.config.option", "some-value") \
-  .getOrCreate()
-{% endhighlight %}
+The entry point into all functionality in Spark is the [`SparkSession`](api/python/pyspark.sql.html#pyspark.sql.SparkSession) class. To create a basic `SparkSession`, just use `SparkSession.builder`:
 
+{% include_example init_session python/sql.py %}
 </div>
 
 <div data-lang="r"  markdown="1">