Add i18l support for Mustache templates (finally)

Format after using AtomicLoader_FilesystemLoader->expandTranslationMarkup():

- basic (((String to {{translate}}))
- plurals: ((({{var_to_check_against}} ? Singular {{value}} : Plural {{value}})))

See commit: 906c1efb34c23ef63b20ddd447e5da5c1fd74dff of
[Mustache Atomic Loader](https://github.com/attitude/mustache-atomic-loader)