Enrich and optimize admin api

1. Provides more admin APIs, such as createTopicInCluster, createSubscriptionGroup, etc.

Currently, only supports two apis:

``` go
type Admin interface {
CreateTopic(ctx context.Context, opts ...OptionCreate) error
DeleteTopic(ctx context.Context, opts ...OptionDelete) error
//TODO
//TopicList(ctx context.Context, mq *primitive.MessageQueue) (*remote.RemotingCommand, error)
//GetBrokerClusterInfo(ctx context.Context) (*remote.RemotingCommand, error)
Close() error
}
```

2. Admin API uses Option Builder Pattern, this will result in many Option Helper functions with the potential for naming conflicts. With more APIs, it becomes harder to maintain.