[SPARK-7255] [STREAMING] [DOCUMENTATION] Added documentation for spark.streaming.kafka.maxRetries

Added documentation for spark.streaming.kafka.maxRetries

Author: BenFradet <benjamin.fradet@gmail.com>

Closes #5808 from BenFradet/master and squashes the following commits:

cc72e7a [BenFradet] updated doc for spark.streaming.kafka.maxRetries to explain the default value
18f823e [BenFradet] Added "consecutive" to the spark.streaming.kafka.maxRetries doc
597fdeb [BenFradet] Mention that spark.streaming.kafka.maxRetries only applies to the direct kafka api
0efad39 [BenFradet] Added documentation for spark.streaming.kafka.maxRetries