SPARK-6992 : Fix documentation example for Spark SQL on StructType

This patch is fixing the Java examples for Spark SQL when defining
programmatically a Schema and mapping Rows.

Author: Olivier Girardot <o.girardot@lateral-thoughts.com>

Closes #5569 from ogirardot/branch-1.3 and squashes the following commits:

c29e58d [Olivier Girardot] SPARK-6992 : Fix documentation example for Spark SQL on StructType

(cherry picked from commit c9b1ba4b16a7afe93d45bf75b128cc0dd287ded0)
Signed-off-by: Reynold Xin <rxin@databricks.com>