Loading Config failure now error, Warn if file doesnt exist [GRAILS-11320]

The default log4j config for a new application restricts grails commons errors to error and not warn. This means if you have a failure in loading an external Config.groovy on your application, there is not message in the logs communicating that failure. In some cases it is legitimate to not load a Config.groovy (for example if it does not exist). And that should be a WARN. But, If the ConfigSlurper runs into a compile exception on the config itself, an error should be thrown. Related to [GRAILS-11320]