feat(template): add elcolio/etcd template

[G07cha]

I've tested it and the container has been created fine and there were no errors in logs but there might be few missing points. I'm not sure about advertise-client-urls and initial-advertise-peer-urls flags, which is required for cluster mode, I haven't found the syntax for flags so I'm assuming it's not supported right now.

Fixes #61