SPARK-1352: Improve robustness of spark-submit script

1. Better error messages when required arguments are missing.
2. Support for unit testing cases where presented arguments are invalid.
3. Bug fix: Only use environment varaibles when they are set (otherwise will cause NPE).
4. A verbose mode to aid debugging.
5. Visibility of several variables is set to private.
6. Deprecation warning for existing scripts.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #271 from pwendell/spark-submit and squashes the following commits:

9146def [Patrick Wendell] SPARK-1352: Improve robustness of spark-submit script
[SQL] Rewrite join implementation to allow streaming of one relation.

Before we were materializing everything in memory.  This also uses the projection interface so will be easier to plug in code gen (its ported from that branch).

@rxin @liancheng

Author: Michael Armbrust <michael@databricks.com>

Closes #250 from marmbrus/hashJoin and squashes the following commits:

1ad873e [Michael Armbrust] Change hasNext logic back to the correct version.
8e6f2a2 [Michael Armbrust] Review comments.
1e9fb63 [Michael Armbrust] style
bc0cb84 [Michael Armbrust] Rewrite join implementation to allow streaming of one relation.