Automatically retrieve device's room/function from CCU and pass as labels

[flammermann]

• Instead of just names, also get rooms and functions for channels.
• Aggregate rooms and functions to device level.
• Make aggregated rooms and functions available as metric labels.
• Change names of command line arguments to match new definition. [breaking change]
• Change keys of labels to make usage clearer. [breaking change]
• Add documentation in README.
• Update sample configuration to show expected format.