[SPARK-15396][SQL][DOC] It can't connect hive metastore database

#### What changes were proposed in this pull request?
The `hive.metastore.warehouse.dir` property in hive-site.xml is deprecated since Spark 2.0.0. Users might not be able to connect to the existing metastore if they do not use the new conf parameter `spark.sql.warehouse.dir`.

This PR is to update the document and example for explaining the latest changes in the configuration of default location of database.

Below is the screenshot of the latest generated docs:

<img width="681" alt="screenshot 2016-05-20 08 38 10" src="https://cloud.githubusercontent.com/assets/11567269/15433296/a05c4ace-1e66-11e6-8d2b-73682b32e9c2.png">

<img width="789" alt="screenshot 2016-05-20 08 53 26" src="https://cloud.githubusercontent.com/assets/11567269/15433734/645dc42e-1e68-11e6-9476-effc9f8721bb.png">

<img width="789" alt="screenshot 2016-05-20 08 53 37" src="https://cloud.githubusercontent.com/assets/11567269/15433738/68569f92-1e68-11e6-83d3-ef5bb221a8d8.png">

No change is made in the R's example.

<img width="860" alt="screenshot 2016-05-20 08 54 38" src="https://cloud.githubusercontent.com/assets/11567269/15433779/965b8312-1e68-11e6-8bc4-53c88ceacde2.png">

#### How was this patch tested?
N/A

Author: gatorsmile <gatorsmile@gmail.com>

Closes #13225 from gatorsmile/document.