Zk kafka plugins

Add a zookeeper config plugin to load json string config from zookeeper;

Add a kafka log receiver plugin, the plugin can only send messages less then 900 Bytes each time. The plugin is not actually practical at the moment, may someone help to figure out a proper way to code with LibKafka.

Yours,
Imcom
I will do some tests on this and previous ones. It seems to me that the kafka lib will do the free() on all related structures once the ~ProduceRequest gets called