Сontainer name vs service name distinction in dsh

[lmakarov]

Review and update the terminology around container vs service in dsh | dsh help.
Most of dsh commands involve a service name as an argument and not a container name - this has to be clearly communicated.

Aslo, dsh ps (which triggers docker-compose ps) lists container names instead of service names, which is confusion for newcomers. This need to be reported upstream as a improvement suggestion.

[achekulaev]

Documentation is updated in development branch.
Request sent to upstream team here: docker/compose#2369