[MINOR][DOCUMENTATION] Fix some minor descriptions in functions consistently with expressions

## What changes were proposed in this pull request?

This PR proposes to improve documentation and fix some descriptions equivalent to several minor fixes identified in https://github.com/apache/spark/pull/15677

Also, this suggests to change `Note:` and `NOTE:` to `.. note::` consistently with the others which marks up pretty.

## How was this patch tested?

Jenkins tests and manually.

For PySpark, `Note:` and `NOTE:` to `.. note::` make the document as below:

**From**

![2016-11-04 6 53 35](https://cloud.githubusercontent.com/assets/6477701/20002648/42989922-a2c5-11e6-8a32-b73eda49e8c3.png)
![2016-11-04 6 53 45](https://cloud.githubusercontent.com/assets/6477701/20002650/429fb310-a2c5-11e6-926b-e030d7eb0185.png)
![2016-11-04 6 54 11](https://cloud.githubusercontent.com/assets/6477701/20002649/429d570a-a2c5-11e6-9e7e-44090f337e32.png)
![2016-11-04 6 53 51](https://cloud.githubusercontent.com/assets/6477701/20002647/4297fc74-a2c5-11e6-801a-b89fbcbfca44.png)
![2016-11-04 6 53 51](https://cloud.githubusercontent.com/assets/6477701/20002697/749f5780-a2c5-11e6-835f-022e1f2f82e3.png)

**To**

![2016-11-04 7 03 48](https://cloud.githubusercontent.com/assets/6477701/20002659/4961b504-a2c5-11e6-9ee0-ef0751482f47.png)
![2016-11-04 7 04 03](https://cloud.githubusercontent.com/assets/6477701/20002660/49871d3a-a2c5-11e6-85ea-d9a5d11efeff.png)
![2016-11-04 7 04 28](https://cloud.githubusercontent.com/assets/6477701/20002662/498e0f14-a2c5-11e6-803d-c0c5aeda4153.png)
![2016-11-04 7 33 39](https://cloud.githubusercontent.com/assets/6477701/20002731/a76e30d2-a2c5-11e6-993b-0481b8342d6b.png)
![2016-11-04 7 33 39](https://cloud.githubusercontent.com/assets/6477701/20002731/a76e30d2-a2c5-11e6-993b-0481b8342d6b.png)

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #15765 from HyukjinKwon/minor-function-doc.