Log analysis: switch from matomo to ELK stack

[dr0i]

Matomo is superslow, 200 lines/sec import.
As the backend is mysqld, this too don't scale nicely. Also eats harddisk away.
The Elastic stack, formerly known as ELK stack, should work smarter, and seems also DSVGO compatible, see https://www.elastic.co/de/webinars/gdpr-compliance-and-elasticsearch.

This is issue has low priority but it should be a reminder, should we make some more bad experiences with matomo, to switch.

Resulting from hbz/lobid-resources#799.