simple interactive cli, move set_power to a separate script/module

This introduces a bit of modularity to the lights_off,lights_on, scripts, but the majority of the commit is an extra simple demo interactive script. It can be extended if need be, but is more of an example of bulb_label and power logic than a CLI in general at the moment.

Please let me know if this commit isn't something you'd like in your repo; I find it a useful primer, but you may not.