[streaming][SPARK-1578] Removed requirement for TTL in StreamingContext.

Since shuffles and RDDs that are out of context are automatically cleaned by Spark core (using ContextCleaner) there is no need for setting the cleaner TTL while creating a StreamingContext.

Author: Tathagata Das <tathagata.das1565@gmail.com>

Closes #491 from tdas/ttl-fix and squashes the following commits:

cf01dc7 [Tathagata Das] Removed requirement for TTL in StreamingContext.
[FIX: SPARK-1376] use --arg instead of --args in SparkSubmit to avoid warning messages

Even if users use `--arg`, `SparkSubmit` still uses `--args` for child args internally, which triggers a warning message that may confuse users:

~~~
--args is deprecated. Use --arg instead.
~~~

@sryza Does it look good to you?

Author: Xiangrui Meng <meng@databricks.com>

Closes #485 from mengxr/submit-arg and squashes the following commits:

5e1b9fe [Xiangrui Meng] update test
cebbeb7 [Xiangrui Meng] use --arg instead of --args in SparkSubmit to avoid warning messages
SPARK-1562 Fix visibility / annotation of Spark SQL APIs

Author: Michael Armbrust <michael@databricks.com>

Closes #489 from marmbrus/sqlDocFixes and squashes the following commits:

acee4f3 [Michael Armbrust] Fix visibility / annotation of Spark SQL APIs