Update the Elastic Data Processing (EDP) documentation page

* Add description of MapReduce.Streaming job type
* Add description of Spark job type
* Add reference to advanced configuration for Swfit proxy
* Note that .sahara suffix is added to Swift URLs automatically
* A few minor changes

Closes-Bug: 1374574
Closes-Bug: 1374606
Change-Id: Ie53888975ce436439cc808b2fdc45dff66bae1a9
(cherry picked from commit 7973db35e61b0c2d686798cb2de50d281713b03b)