### 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?
- Sets up links between related sections.
- Add "Related sections" for each section.
- Change to the left hand side menu to reflect the current status of the doc.
- Other minor cleanups.
### Why are the changes needed?
Currently Spark lacks documentation on the supported SQL constructs causing
confusion among users who sometimes have to look at the code to understand the
usage. This is aimed at addressing this issue.
### Does this PR introduce any user-facing change?
Yes.
### How was this patch tested?
Tested using jykyll build --serve
Closes#27371 from dilipbiswal/select_finalization.
Authored-by: Dilip Biswal <dkbiswal@gmail.com>
Signed-off-by: Sean Owen <srowen@gmail.com>
### What changes were proposed in this pull request?
Document CLUSTER BY clause of SELECT statement in SQL Reference Guide.
### Why are the changes needed?
Currently Spark lacks documentation on the supported SQL constructs causing
confusion among users who sometimes have to look at the code to understand the
usage. This is aimed at addressing this issue.
### Does this PR introduce any user-facing change?
Yes.
**Before:**
There was no documentation for this.
**After.**
<img width="972" alt="Screen Shot 2020-01-20 at 2 59 05 PM" src="https://user-images.githubusercontent.com/14225158/72762704-7528de80-3b95-11ea-9d34-8fa0ab63d4c0.png">
<img width="972" alt="Screen Shot 2020-01-20 at 2 59 19 PM" src="https://user-images.githubusercontent.com/14225158/72762710-78bc6580-3b95-11ea-8279-2848d3b9e619.png">
### How was this patch tested?
Tested using jykyll build --serve
Closes#27297 from dilipbiswal/sql-ref-select-clusterby.
Authored-by: Dilip Biswal <dkbiswal@gmail.com>
Signed-off-by: Sean Owen <srowen@gmail.com>
