Add multiple executors

Refactoring / clean up
Adding executors instead of framework messages
reloadConfig could really come out of the JN-specific code, since it's a prerequisite for all of them.
In fact, why do you even need to call reloadConfig here? The fetcher should pull it down into the sandbox already, since it's in ExecutorInfo's URIs. Do you just need to copy it to a predefined location, or start the hdfs processes by pointing them to the location in the sandbox?