Feature: Be able to specify which services to start

[davidkarlsen]

It would be great if the API could expose a method to select which services to start (e.g. docker-compose up serviceX serviceY.

The reason for this is that I want to avoid duplicating / splitting up compose files - but use the same compose-files for a few different contexts - one is to run the full stack launched manually, another is to run a sub-set of services through docker-compose-rule.