extdata: show debug message if external command exits with non-zero status
This isn't fatal because it's quite common for grep to exit with 1. Thanks to
Foozy for spotting this.
templatekw: allow accessing to nested namespace item by its template name
Since we have the dot operator, it makes more sense to write
{namespaces.tags % "{tag}"}
instead of
{namespaces.tags % "{name}"}