## What changes were proposed in this pull request?

I search the whole documents directory using SQLContext, and update the following places:

- docs/configuration.md, sparkR code snippets.
- docs/streaming-programming-guide.md, several example code.

## How was this patch tested?

N/A

Author: WeichenXu <WeichenXu123@outlook.com>

Closes #14025 from WeichenXu123/WIP_SQLContext_update.