[ISSUE #176] Support manage multi cluster

[drivebyer]

What is the purpose of the change

In order to manage multi cluster by one operator.

task1 && task2 of https://github.com/apache/rocketmq-operator/issues/176

Brief changelog

XX

Verifying this change

1. tested against old cluster()

2. tested against creating two cluster in one namespace yaml1(set rocketmq cluster name to empty string): https://gist.github.com/drivebyer/8795a96966be4fd6ebf395cc347a159d yaml2(set rocketmq cluster name to test-rocketmq): https://gist.github.com/drivebyer/338a0cba168249dd3c02ce0f33f775d8

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[drivebyer]

@caigy PTAL

[drivebyer]

It seems that there're lots of modifications in this pr, you'd better add some doc for your design, especially for the changes in CRs reflecting the status of all modules in the RocketMQ cluster.

OK, i would add this.