* Introduce jaxrs-cxf-client-jackson-nullable sample
Generated using: ./bin/generate-samples.sh bin/configs/other/openapi3/jaxrs-cxf-client-jackson-nullable.yaml
* Add support for openApiNullable to JavaCXFClientCodegen
Add import mapping for JsonNullable to AbstractJavaCodegen
* Deduplicate string "jackson" in generators extending AbstractJavaCodegen
* Adjust nullable fields
* Adjust standard getters for nullable fields
add @JsonIgnore to standard getters
* Adjust standard setters for nullable fields
* Adjust fluent setter for nullable fields
* Introduce distinct getter and setter for nullable fields
* Adjust add method for nullable lists
* Adjust put method for nullable maps
* Cleanup JavaJaxRS/cxf/pojo.mustache
* Further cleanup JavaJaxRS/cxf/pojo.mustache
* Adjust inner enum getters
