Extend splunk modules to allow cluster role configuration

Please forgive me if these changes are the wrong direction in terms of best practices, etc. I was unable to find how to do exactly what I wanted. As things stand now, both the splunk and splunk::foo classes need to be included in a node definition for the role to be properly configured. It's been a while since I've touched Puppet, so I am most definitely rusty.

This request exposes the necessary class parameters to create a splunk cluster with a master indexer, additional index peers and search heads. This allows the class to be used in ENC tools fairly easily. 

Please review, comment and/or provide any suggestions.

Thanks!

Matt