[SPARK-2260] Fix standalone-cluster mode, which was broken

The main thing was that spark configs were not propagated to the driver, and so applications that do not specify `master` or `appName` automatically failed. This PR fixes that and a couple of miscellaneous things that are related.

One thing that may or may not be an issue is that the jars must be available on the driver node. In `standalone-cluster` mode, this effectively means these jars must be available on all the worker machines, since the driver is launched on one of them. The semantics here are not the same as `yarn-cluster` mode,  where all the relevant jars are uploaded to a distributed cache automatically and shipped to the containers. This is probably not a concern, but still worth a mention.
Not super important, but Yarn only uses system properties for configs needed to open the akka connection and then transfer the whole config. See: https://github.com/apache/spark/blob/master/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnableUtil.scala#L65

Might be worth doing the same here, or coalescing that logic somewhere.