Create and maintain multiple Elasticsearch indexes

**Is your feature request related to a problem? Please describe.**
Users like "human-readable" fields (and values) in a search interface. Currently, the Typed PID Maker is providing a purely machine-readable index.

**Describe the solution you'd like**
I'd like to have an option to create and maintain an Elasticsearch index with human-readable field. Therefore, I would like to have a configuration option where I can specify the index name of the human-readable index and the index name of the machine-readable index. If a value is not provided, this index should not be created and maintained.

Start by locating the Typed PID Maker's Elasticsearch index configuration and the code that creates and maintains its current machine-readable index. Trace how index names are supplied and how updates are applied, then verify the optional human-readable index behavior for configurations with one or both index names. Done means both indexes can be independently configured and maintained without creating an omitted index.

Written by the indexing model from the issue text.