Provide better default Json mapperFactory for saveAsElasticSearch

[kellen]

Current default is SimpleJsonpMapper which is practically useless, perhaps the value used in the example would be more appropriate?

() => {
        // Use jackson for user json serialization
        val mapper = new JacksonJsonpMapper()
        // Add scala support
        mapper.objectMapper().registerModule(DefaultScalaModule)
        // Add java.time support
        mapper.objectMapper().registerModule(new JavaTimeModule())
        mapper
      }