DdlImporter throws illegal arg exceptions if model name is empty. Should be validation error and message in SelectTranslatorAndTargetPage

Setting the ddl source model name to non-null, then deleting the name results in an Illegal Arg exception rather than just an ERROR on the page (SelectTranslatorAndTargetPage)

The DdlImporter is doing arg/validation checks in setModelName() but seems like the DdlImporter should create a MultiStatus() which can be used by the importer UI to show .... the status rather then throw/catch an exception