Create function to gather debug info

[hafen]

Add an exported, documented function to RHIPE, call it maybe rhipeDebugInfo() that runs a MapReduce job that returns for each map task a list with the following:

• hostname: host name of the machine - I suppose through something like system("hostname", intern = TRUE)
• user: name of the user running the R process - use something like system("whoami", intern = TRUE)
• env: a list of environment variables, through Sys.getenv()
• libPaths: the result of calling .libPaths()
• sessionInfo: the result of calling sessionInfo()

Anything else?

The trick is to make it run a dummy job that we can ensure will run on all nodes of the cluster, but only a small number (preferably one) task per node.

This will be a useful function to expose to any RHIPE user to be able to run to figure out why something might not be working, or to provide details about their system.

[hafen]

It would be good to put it in both master and dev.