allow unknown features

org.fortiss.tooling.kernel/trunk/src/org/fortiss/tooling/kernel/internal/MigrationService.java

@@ -70,7 +70,7 @@ public class MigrationService extends ObjectAwareServiceBase<IMigrationProvider>
 					provider.migrate(input, unknownFeatures);
 				}
 				if(!unknownFeatures.isEmpty()) {
-					throw new RuntimeException(input.getSaveableName() +
+					error(ToolingKernelActivator.getDefault(), input.getSaveableName() +
 							" contains one or more unknown feature(s): " +
 							featuresToStrings(unknownFeatures));
 				}