Major Description
Currently, TopicCommand has the following inconsistencies.
1. The topic arg is optional in list topic, but not in describe topic.
2. The topics-with-overrides option is available in list topic, but not in describe topic.
3. It's also a bit weird that if the topics-with-overrides option is specified, list topics returns more than just a list of topics (it prints out the config, replication factor, etc).