Puppet Lookup should be easily used as a library in other applications

Currently in PE, the pe_infrastructure and pe_manager modules end up recreated a large amount of the puppet lookup application logic to do lookups without shelling out to puppet (which would be expensive). It would be far better if puppet itself exposed the lookup as an easy to use method for other applications. Ideally, if I knew the node name, environment name, and a list of keys to lookup, I should be able to invoke the method to retrieve those lookups.