Refactor creation of line in sources

At the moment the number of line in sources is hard coded. The creation of these sources is also hard coded in liquidsoap. I propose a list based approach when we switch to yaml based configuration files. A line in could then look something like this:

input_devices:
  - "default"
  - "default"

Dependencies

• Config consolidation: Use YAML instead of INI file (#41 - closed)