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
That didn't compile for me.  As far as I can tell you can't do pattern matching on strings in that way.  Switching it to something that looks a little prettier.  Let me know if I'm missing anything.