## What changes were proposed in this pull request?

**1.stage api modify the description format**
<td>A list of all stages for a given application.</td>
<br><code>?status=[active|complete|pending|failed]</code> list only stages in the state.
content should be included in <td> </ td>

fix before:
![1](https://user-images.githubusercontent.com/26266482/31753100-201f3432-b4c1-11e7-9e8d-54b62b96c17f.png)

fix after:
![2](https://user-images.githubusercontent.com/26266482/31753102-23b174de-b4c1-11e7-96ad-fd79d10440b9.png)

**2.add version api doc '/api/v1/version' in monitoring.md**

fix after:
![3](https://user-images.githubusercontent.com/26266482/31753087-0fd3a036-b4c1-11e7-802f-a6dc86a2a4b0.png)

## How was this patch tested?
manual tests

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: guoxiaolong <guo.xiaolong1@zte.com.cn>

Closes #19532 from guoxiaolongzte/SPARK-22311.