Cast-vue

Show them since they are available in [django-cast](https://github.com/ephes/django-cast).

- New type interfaces for facet counts
- npm update..

- better error logging (still far from good)
- send "" instead of null for comment without parent

Added the last two missing features:

- Comments
- Podlove player for audio content

What is working:
- Galleries
- Filter form
- Pagination

Todo:
- comments