Log the launch command for Spark daemons

For debugging and analysis purposes, it's nice to have the exact command
used to launch Spark contained within the logs. This adds the necessary
hooks to make that possible.
Log the launch command for Spark executors
Make output formatting consistent between bash/scala
Using quotes when printing out command
Merge pull request #775 from pwendell/print-launch-command

Log the launch command for Spark daemons