KafkaSpout constructor with KafkaConsumerFactory shoud be public

When we use custom implement of interface "Deserializer"，KafkaSpout constructor can only use class "KafkaConsumerFactoryDefault"，the method “configure” of Interface “Deserializer” will not be called。

We need change the "KafkaSpout" constructor with "KafkaConsumerFactory" to be public, so we can create custom custom implement of interface "KafkaConsumerFactory".