Configuration documentation updates

1. Add < code > to configuration options
2. List env variables in tabular format to be consistent with other pages.
3. Moved Viewing Spark Properties section up.

This is against branch-1.0, but should be cherry picked into master as well.

Author: Reynold Xin <rxin@apache.org>

Closes #851 from rxin/doc-config and squashes the following commits:

28ac0d3 [Reynold Xin] Add <code> to configuration options, and list env variables in a table.

(cherry picked from commit 75af8bd3336d09e8c691e54ae9d2358fe1bf3723)
Signed-off-by: Reynold Xin <rxin@apache.org>
[SPARK-1870] Make spark-submit --jars work in yarn-cluster mode.

Sent secondary jars to distributed cache of all containers and add the cached jars to classpath before executors start. Tested on a YARN cluster (CDH-5.0).

`spark-submit --jars` also works in standalone server and `yarn-client`. Thanks for @andrewor14 for testing!

I removed "Doesn't work for drivers in standalone mode with "cluster" deploy mode." from `spark-submit`'s help message, though we haven't tested mesos yet.

CC: @dbtsai @sryza

Author: Xiangrui Meng <meng@databricks.com>

Closes #848 from mengxr/yarn-classpath and squashes the following commits:

23e7df4 [Xiangrui Meng] rename spark.jar to __spark__.jar and app.jar to __app__.jar to avoid confliction apped $CWD/ and $CWD/* to the classpath remove unused methods
a40f6ed [Xiangrui Meng] standalone -> cluster
65e04ad [Xiangrui Meng] update spark-submit help message and add a comment for yarn-client
11e5354 [Xiangrui Meng] minor changes
3e7e1c4 [Xiangrui Meng] use sparkConf instead of hadoop conf
dc3c825 [Xiangrui Meng] add secondary jars to classpath in yarn
Fix UISuite unit test that fails under Jenkins contention

Due to perhaps zombie processes on Jenkins, it seems that at least 10
Spark ports are in use. It also doesn't matter that the port increases
when used, it could in fact go down -- the only part that matters is
that it selects a different port rather than failing to bind.
Changed test to match this.

Thanks to @andrewor14 for helping diagnose this.

Author: Aaron Davidson <aaron@databricks.com>

Closes #857 from aarondav/tiny and squashes the following commits:

c199ec8 [Aaron Davidson] Fix UISuite unit test that fails under Jenkins contention