Make firstname-lastname reference optional for Person Records

Referenced persons are always summarized by their firstname and lastname properties via https://gitlab.indiscale.com/caosdb/src/caosdb-webui/-/blob/dev/src/core/js/ext_references.js#L276. This breaks the summary if those properties are not present or named differntly.

• Moved to reference-resolver example
• Explained how to configure, extend, and disable the resolver