v1.25.10

Command line API: minor change of some sentinal values

This release comes with some minor command line option changes:

| before             | now             |
|--------------------|-----------------|
| --export ''        | --export .      |
| -x ''              | -x .            |
| --force-lang ''    | --force-lang -  |
| -l ''              | -l -            |

* The new template variable `force_lang` reflects the command line option
  `--force-lang` and shows its influence in templates explicitly.
* The template filter `replace empty` now recognizes empty arrays and the
  `Null` type as empty. Its option `with` accepts now any type.