Provide container name (and/or its number) in environment variables

[valyagolev]

It would be very useful if there was a way to find out the container name (like, projectname_webserver_1) from inside of it, to use it as some kind of an id (like for kafka, or in the logs).

The only way to get it which I could find is by parsing it out from some *_NAME environment variable, which requires the container to have links, and feels bad.

[dnephin]

You can use the hostname as a unique id, which is the unique container id, by using $(hostname).

This issue is a duplicate of #1503