With V6 of elasticsearch the meaning / handling of index and type has
changed, and it will change further in the future.
We therefore move code to own classes and adjust / refactor calling
code.
As some search services, like elasticsearch, allow generation of a
string that should be displayed in frontend, we provide a new getter for
that.
The old existing name can be a fallback in custom implementations.
As TypoScript does not provide a way to configure key less options, we
use a comma separated list and explode them to stay compatible with
elasticsearch.