Add support for add.properties and add.properties.prefix

While using the camel rabbitmq kafka sink connector we had to generate some properties like correlation-id, content-type, content-encoding etc., 

These are also headers. These are treated as special by CamelSinkTask when prefixed with "CamelProperty."

It would be nice to have support for 2 more additional configuration to support Properties

• "add.properties.prefix" -> String with the default value of ""
• "add.properties" => List of properties   => These keys should exist inside the message. The values are picked up from the SinkRecord.
• "add.properties.custom.mapData[key1]": "value1"
• "add.properties.custom.mapData[key2]": "value2"
• "add.properties.custom.mapData[key3]": "value3"

When it is there like this for camel rabbitmq kafka connector, we can set the configuration "add.properties.prefix" to "CamelProperty."