[SPARK-2307] SparkUI - storage tab displays incorrect RDDs

The issue here is that the `StorageTab` listens for updates from the `StorageStatusListener`, but when a block is kicked out of the cache, `StorageStatusListener` removes it from its list. Thus, there is no way for the `StorageTab` to know whether a block has been dropped.

This issue was introduced in #1080, which was itself a bug fix. Here we revert that PR and offer a different fix for the original bug (SPARK-2144).

Author: Andrew Or <andrewor14@gmail.com>

Closes #1249 from andrewor14/storage-ui-fix and squashes the following commits:

af019ce [Andrew Or] Fix SPARK-2307
[SPARK-2259] Fix highly misleading docs on cluster / client deploy modes

The existing docs are highly misleading. For standalone mode, for example, it encourages the user to use standalone-cluster mode, which is not officially supported. The safeguards have been added in Spark submit itself to prevent bad documentation from leading users down the wrong path in the future.

This PR is prompted by countless headaches users of Spark have run into on the mailing list.

Author: Andrew Or <andrewor14@gmail.com>

Closes #1200 from andrewor14/submit-docs and squashes the following commits:

5ea2460 [Andrew Or] Rephrase cluster vs client explanation
c827f32 [Andrew Or] Clarify spark submit messages
9f7ed8f [Andrew Or] Clarify client vs cluster deploy mode + add safeguards
[SPARK-2003] Fix python SparkContext example

Author: Matthew Farrellee <matt@redhat.com>

Closes #1246 from mattf/SPARK-2003 and squashes the following commits:

b12e7ca [Matthew Farrellee] [SPARK-2003] Fix python SparkContext example