[DOCUMENTATION]Fixed Missing Type Import in Documentation

Needed to import the types specifically, not the more general pyspark.sql

Author: Bill Chambers <wchambers@ischool.berkeley.edu>
Author: anabranch <wac.chambers@gmail.com>

Closes #5179 from anabranch/master and squashes the following commits:

8fa67bf [anabranch] Corrected SqlContext Import
603b080 [Bill Chambers] [DOCUMENTATION]Fixed Missing Type Import in Documentation

docs/sql-programming-guide.md

@@ -624,7 +624,8 @@ tuples or lists in the RDD created in the step 1.
 For example:
 {% highlight python %}
 # Import SQLContext and data types
-from pyspark.sql import *
+from pyspark.sql import SQLContext
+from pyspark.sql.types import *
 
 # sc is an existing SparkContext.
 sqlContext = SQLContext(sc)