`dde exec` broken with newest `yq` version

[lukasluecke]

The newest yq version now parses comments in yml files, so the following docker-compose.yml will not work with dde exec anymore:

services:
    web: # Example web service

We should absolutely specify which yq-version to use, but also fix our parsing logic to filter out comments of service definition lines.

Maybe even get rid of it completely, and remove the "default to first service" logic?