SPARK-2662: Fix NPE for JsonProtocol

Author: GuoQiang Li <witgo@qq.com>

Closes #1511 from witgo/JsonProtocol and squashes the following commits:

2b6227f [GuoQiang Li] Fix NPE for JsonProtocol
[SPARK-2658][SQL] Add rule for true = 1.

Author: Michael Armbrust <michael@databricks.com>

Closes #1556 from marmbrus/fixBooleanEqualsOne and squashes the following commits:

ad8edd4 [Michael Armbrust] Add rule for true = 1 and false = 0.
SPARK-2310. Support arbitrary Spark properties on the command line with ...

...spark-submit

The PR allows invocations like
  spark-submit --class org.MyClass --spark.shuffle.spill false myjar.jar

Author: Sandy Ryza <sandy@cloudera.com>

Closes #1253 from sryza/sandy-spark-2310 and squashes the following commits:

1dc9855 [Sandy Ryza] More doc and cleanup
00edfb9 [Sandy Ryza] Review comments
91b244a [Sandy Ryza] Change format to --conf PROP=VALUE
8fabe77 [Sandy Ryza] SPARK-2310. Support arbitrary Spark properties on the command line with spark-submit
[SPARK-2661][bagel]unpersist old processed rdd

Unpersist useless rdd during bagel iteration to make full use of memory.

Author: Daoyuan <daoyuan.wang@intel.com>

Closes #1519 from adrian-wang/bagelunpersist and squashes the following commits:

182c9dd [Daoyuan] rename var nextUseless to lastRDD
87fd3a4 [Daoyuan] bagel unpersist old processed rdd