## What changes were proposed in this pull request?
1, `**Example**` => `**Examples**`, because more algos use `**Examples**`.
2,  delete `### Examples` in `Isotonic regression`, because it's not that special in http://spark.apache.org/docs/latest/ml-classification-regression.html
3, add missing marks for `LDA` and other algos.

## How was this patch tested?
No tests for it only modify doc

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #15783 from zhengruifeng/doc_fix.

## What changes were proposed in this pull request?

Made DataFrame-based API primary
* Spark doc menu bar and other places now link to ml-guide.html, not mllib-guide.html
* mllib-guide.html keeps RDD-specific list of features, with a link at the top redirecting people to ml-guide.html
* ml-guide.html includes a "maintenance mode" announcement about the RDD-based API
  * **Reviewers: please check this carefully**
* (minor) Titles for DF API no longer include "- spark.ml" suffix.  Titles for RDD API have "- RDD-based API" suffix
* Moved migration guide to ml-guide from mllib-guide
  * Also moved past guides from mllib-migration-guides to ml-migration-guides, with a redirect link on mllib-migration-guides
  * **Reviewers**: I did not change any of the content of the migration guides.

Reorganized DataFrame-based guide:
* ml-guide.html mimics the old mllib-guide.html page in terms of content: overview, migration guide, etc.
* Moved Pipeline description into ml-pipeline.html and moved tuning into ml-tuning.html
  * **Reviewers**: I did not change the content of these guides, except some intro text.
* Sidebar remains the same, but with pipeline and tuning sections added

Other:
* ml-classification-regression.html: Moved text about linear methods to new section in page

## How was this patch tested?

Generated docs locally

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #14213 from jkbradley/ml-guide-2.0.

## What changes were proposed in this pull request?

Correct some typos and incorrectly worded sentences.

## How was this patch tested?

Doc changes only.

Note that many of these changes were identified by whomfire01

Author: sethah <seth.hendrickson16@gmail.com>

Closes #13180 from sethah/ml_guide_audit.

## What changes were proposed in this pull request?

(Please fill in changes proposed in this fix)

Add guide doc and examples for GaussianMixture in Spark.ml in Java, Scala and Python.

## How was this patch tested?

(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)

Manual compile and test all examples

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #12788 from wangmiao1981/example.

## What changes were proposed in this pull request?

(Please fill in changes proposed in this fix)
The generated document has the incorrect format for biseckmeans.

![bug](https://cloud.githubusercontent.com/assets/5033592/15233120/d910098a-185a-11e6-901d-44aeafc8a011.jpg)

## How was this patch tested?

(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)

Fix the formatting.
![fix](https://cloud.githubusercontent.com/assets/5033592/15233136/fce2ccd0-185a-11e6-9ded-14d71da4bdab.jpg)

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #13083 from wangmiao1981/doc.

## What changes were proposed in this pull request?
1,create a libsvm-type dataset for lda: `data/mllib/sample_lda_libsvm_data.txt`
2,add python example
3,directly read the datafile in examples
4,BTW, change to `SparkSession` in `aft_survival_regression.py`

## How was this patch tested?
manual tests
`./bin/spark-submit examples/src/main/python/ml/lda_example.py`

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12927 from zhengruifeng/lda_pe.

## What changes were proposed in this pull request?
Python example for ml.kmeans already exists, but not included in user guide.
1,small changes like: `example_on` `example_off`
2,add it to user guide
3,update examples to directly read datafile

## How was this patch tested?
manual tests
`./bin/spark-submit examples/src/main/python/ml/kmeans_example.py

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12925 from zhengruifeng/km_pe.

## What changes were proposed in this pull request?

1, add BisectingKMeans to ml-clustering.md
2, add the missing Scala BisectingKMeansExample
3, create a new datafile `data/mllib/sample_kmeans_data.txt`

## How was this patch tested?

manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #11844 from zhengruifeng/doc_bkm.

cc jkbradley

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #10244 from yu-iskw/SPARK-12215.

[SPARK-12212][ML][DOC] Clarifies the difference between spark.ml, spark.mllib and mllib in the documentation.

Replaces a number of occurences of `MLlib` in the documentation that were meant to refer to the `spark.mllib` package instead. It should clarify for new users the difference between `spark.mllib` (the package) and MLlib (the umbrella project for ML in spark).

It also removes some files that I forgot to delete with #10207

Author: Timothy Hunter <timhunter@databricks.com>

Closes #10234 from thunterdb/12212.

This PR moves pieces of the spark.ml user guide to reflect suggestions in SPARK-8517. It does not introduce new content, as requested.

<img width="192" alt="screen shot 2015-12-08 at 11 36 00 am" src="https://cloud.githubusercontent.com/assets/7594753/11666166/e82b84f2-9d9f-11e5-8904-e215424d8444.png">

Author: Timothy Hunter <timhunter@databricks.com>

Closes #10207 from thunterdb/spark-8517.

jira: https://issues.apache.org/jira/browse/SPARK-11689

Add simple user guide for LDA under spark.ml and example code under examples/. Use include_example to include example code in the user guide markdown. Check SPARK-11606 for instructions.

Original PR is reverted due to document build error. https://github.com/apache/spark/pull/9722

mengxr feynmanliang yinxusen  Sorry for the troubling.

Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #9974 from hhbyyh/ldaMLExample.

This reverts commit e359d5dc.

jira: https://issues.apache.org/jira/browse/SPARK-11689

Add simple user guide for LDA under spark.ml and example code under examples/. Use include_example to include example code in the user guide markdown. Check SPARK-11606 for instructions.

Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #9722 from hhbyyh/ldaMLExample.