Remove the watches/broker for new topics and partitions and change create topic admin API to send start replica state change to all brokers

Currently in 0.8, all brokers register a watch on /brokers/topics and /brokers/topics/[topic] for all topics in a Kafka cluster. The watches are required to discover new topics.
There is another way this can be achieved, as proposed here - https://cwiki.apache.org/confluence/display/KAFKA/Kafka+replication+detailed+design+V2#KafkareplicationdetaileddesignV2-Createtopic

Basically, the create-topic admin command sends start-replica state change request to all brokers in the assigned replicas list.