Improve error message

[mfaughn]

I was getting an error that follows the pattern, "Unable to find ImplementationGuide.definition.resource.name for the resource . Name is mandatory if it cannot be inferred from the resource to allow proper population of the artifact list."

The offending resource has a name. This error was actually caused by the resource not having a title. It would be helpful if the error message correctly identified the problem.

[lmckenzi]

Change the second sentence of the message to "ImplementationGuide.resource.name is mandatory if it cannot be inferred from the referenced resource (i.e. the resource.title) to allow proper population of the artifact list"