[SPARK-16303][DOCS][EXAMPLES] Updated SQL programming guide and examples

- Hard-coded Spark SQL sample snippets were moved into source files under examples sub-project.
- Removed the inconsistency between Scala and Java Spark SQL examples
- Scala and Java Spark SQL examples were updated

The work is still in progress. All involved examples were tested manually. An additional round of testing will be done after the code review.

![image](https://cloud.githubusercontent.com/assets/6235869/16710314/51851606-462a-11e6-9fbe-0818daef65e4.png)

Author: aokolnychyi <okolnychyyanton@gmail.com>

Closes #14119 from aokolnychyi/spark_16303.