[SPARK-7284] [STREAMING] Updated streaming documentation

- Kinesis API updated
- Kafka version updated, and Python API for Direct Kafka added
- Added SQLContext.getOrCreate()
- Added information on how to get partitionId in foreachRDD

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

Closes #6781 from tdas/SPARK-7284 and squashes the following commits:

aac7be0 [Tathagata Das] Added information on how to get partition id
a66ec22 [Tathagata Das] Complete the line incomplete line,
a92ca39 [Tathagata Das] Updated streaming documentation