[SPARK-3412] [PySpark] Replace Epydoc with Sphinx to generate Python API docs

Retire Epydoc, use Sphinx to generate API docs.

Refine Sphinx docs, also convert some docstrings into Sphinx style.

It looks like:
![api doc](https://cloud.githubusercontent.com/assets/40902/4538272/9e2d4f10-4dec-11e4-8d96-6e45a8fe51f9.png)

Author: Davies Liu <davies.liu@gmail.com>

Closes #2689 from davies/docs and squashes the following commits:

bf4a0a5 [Davies Liu] fix links
3fb1572 [Davies Liu] fix _static in jekyll
65a287e [Davies Liu] fix scripts and logo
8524042 [Davies Liu] Merge branch 'master' of github.com:apache/spark into docs
d5b874a [Davies Liu] Merge branch 'master' of github.com:apache/spark into docs
4bc1c3c [Davies Liu] refactor
746d0b6 [Davies Liu] @param -> :param
240b393 [Davies Liu] replace epydoc with sphinx doc

1 files changed, 4 insertions, 4 deletions

diff --git a/docs/README.md b/docs/README.md
index 79708c3df9..0facecdd5f 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -54,19 +54,19 @@ phase, use the following sytax:
     // supported languages too.
     {% endhighlight %}
 
-## API Docs (Scaladoc and Epydoc)
+## API Docs (Scaladoc and Sphinx)
 
 You can build just the Spark scaladoc by running `sbt/sbt doc` from the SPARK_PROJECT_ROOT directory.
 
-Similarly, you can build just the PySpark epydoc by running `epydoc --config epydoc.conf` from the
-SPARK_PROJECT_ROOT/pyspark directory. Documentation is only generated for classes that are listed as
+Similarly, you can build just the PySpark docs by running `make html` from the
+SPARK_PROJECT_ROOT/python/docs directory. Documentation is only generated for classes that are listed as
 public in `__init__.py`.
 
 When you run `jekyll` in the `docs` directory, it will also copy over the scaladoc for the various
 Spark subprojects into the `docs` directory (and then also into the `_site` directory). We use a
 jekyll plugin to run `sbt/sbt doc` before building the site so if you haven't run it (recently) it
 may take some time as it generates all of the scaladoc.  The jekyll plugin also generates the
-PySpark docs using [epydoc](http://epydoc.sourceforge.net/).
+PySpark docs [Sphinx](http://sphinx-doc.org/).
 
 NOTE: To skip the step of building and copying over the Scala and Python API docs, run `SKIP_API=1
 jekyll`.