* add NodeTypeFromDatasourceUID and DataSourceModelFromNodeType() * deprecate expr.DataSourceModel * replace usages of IsDataSource to NodeTypeFromDatasourceUID * replace usages of DataSourceModel to DataSourceModelFromNodeType()
* add NodeTypeFromDatasourceUID and DataSourceModelFromNodeType() * deprecate expr.DataSourceModel * replace usages of IsDataSource to NodeTypeFromDatasourceUID * replace usages of DataSourceModel to DataSourceModelFromNodeType()