Add admin API operations to promisified and non-promisified API

[milindl]

For example: listing topics, ACL operations, consumer group operations, consumer group offset operations.

[milindl]

Added: ListGroups to list consumer groups

[milindl]

Added: DeleteGroups and DescribeGroups
Added: ListTopics

[brunodomenici]

+1 for describeGroup. We use this function to health check the consumer.
Any idea how to do it without this function?

[milindl]

@brunodomenici , the function is already available in the released version of the library which you can download off npm.

Unfortunately I've not added an example yet, but the usage can be seen in the test: https://github.com/confluentinc/confluent-kafka-javascript/blob/v0.1.12-devel/test/promisified/admin/describe_groups.spec.js#L71