### What changes were proposed in this pull request?
Change the link to the Scala API document.
```
$ git grep "#org.apache.spark.package"
docs/_layouts/global.html: <li><a href="api/scala/index.html#org.apache.spark.package">Scala</a></li>
docs/index.md:* [Spark Scala API (Scaladoc)](api/scala/index.html#org.apache.spark.package)
docs/rdd-programming-guide.md:[Scala](api/scala/#org.apache.spark.package), [Java](api/java/), [Python](api/python/) and [R](api/R/).
```
### Why are the changes needed?
The home page link for Scala API document is incorrect after upgrade to 3.0
### Does this PR introduce any user-facing change?
Document UI change only.
### How was this patch tested?
Local test, attach screenshots below:
Before:
After:
Closes#27549 from xuanyuanking/scala-doc.
Authored-by: Yuanjian Li <xyliyuanjian@gmail.com>
Signed-off-by: Sean Owen <srowen@gmail.com>
### What changes were proposed in this pull request?
Standardize sql reference
### Why are the changes needed?
To have consistent docs
### Does this PR introduce any user-facing change?
Yes
### How was this patch tested?
Tested using jykyll build --serve
Closes#26721 from huaxingao/spark-30085.
Authored-by: Huaxin Gao <huaxing@us.ibm.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>
### What changes were proposed in this pull request?
Document REFRESH TABLE statement in the SQL Reference Guide.
### Why are the changes needed?
Currently there is no documentation in the SPARK SQL to describe how to use this command, it is to address this issue.
### Does this PR introduce any user-facing change?
Yes.
#### Before:
There is no documentation for this.
#### After:
<img width="826" alt="Screen Shot 2019-09-12 at 11 39 21 AM" src="https://user-images.githubusercontent.com/7550280/64811385-01752600-d552-11e9-876d-91ebb005b851.png">
### How was this patch tested?
Using jykll build --serve
Closes#25549 from kevinyu98/spark-28828-refreshTable.
Authored-by: Kevin Yu <qyu@us.ibm.com>
Signed-off-by: Xiao Li <gatorsmile@gmail.com>
