Document HostAndPortMapper usage

[ggivo]

Feature Request

The team should improve documentation around use cases & how to use redis.clients.jedis.HostAndPortMapper

Initially requested in #3298 (comment)

There are a multitude of questions around how to use Jedis with Docker/Kubernetes environment, which also will benefit.

Describe the solution you'd like

• Add Javadoc
• Add documentation & provide example usage in http://github.com/redis/jedis/wiki

[JuneYub]

I'd like to work on this issue.