Implement toString method in ResourceLocator

When injecting method parameters fails in org.jboss.resteasy.core.MethodInjectorImpl#injectArguments because of an exception thrown by some ParameterConverter an error message is generated that should contain the method the injection failed for. The message is created by calling method.toString() which just returns the default toString from java.lang.Object. The message would be much more helpful when the toString method would be overridden in org.jboss.resteasy.spi.metadata.ResourceLocator.