Series language pages
DistroSeriesLanguage and ProductSeriesLanguage pages have several common properties:
They display a list of all POFiles in a particular context (i.e. DistroSeries or ProductSeries) for a single language.
- Their contexts implement IHasTranslationTemplates and IRosettaStats
We should:
Migrate them to 3.0 templates (#423836)
- Introduce IHasTranslationFiles interface and abstract implementation which works well for both, make DSL and PSL use that
- Introduce cross-batch sorting into these (sort over multiple batches if there's more than meets the eye)
- Implement the same interfaces/templates for source packages
- Implement the same interfaces/templates for projects