feat(datatable): normalize keys for displayValue
feat(datatable): normalize keys for displayValue

accepts now any combination of dot-seperated strings and arrays of those

SpoonX/aurelia-datatable,SpoonX/aurelia-datatable,VMBindraban/aurelia-datatable,nvtin/aurelia-datatable,nvtin/aurelia-datatable,VMBindraban/aurelia-datatable,jeremyvergnas/aurelia-data-table,jeremyvergnas/aurelia-data-table