## What changes were proposed in this pull request?

Updates links to the wiki to links to the new location of content on spark.apache.org.

## How was this patch tested?

Doc builds

Author: Sean Owen <sowen@cloudera.com>

Closes #15967 from srowen/SPARK-18073.1.

(cherry picked from commit 7e0cd1d9)
Signed-off-by: Sean Owen <sowen@cloudera.com>