Add support for KnowGo Adaptation Layer events

[pmundt]

This is an initial attempt at getting notifications from our backend into the system, which we plan to expand with additional events and actions over time.

[CalmBit]

LGTM, aside from the one small documentation point I pointed out. I don't know enough about this personally to approve it, but I can't see anything I'd reject!

[muesli]

Looks good to me, too, apart from @rubiojr's comment. Let's try not to spam the console too much. In the meantime I'm working on a logger module that lets you browse/filter by each bee's individual output. That should improve the situation quite a bit.

[pmundt]

I've now switched it over to the debug logger, as requested.

[muesli]

One issue we got here is depending on http.NewRequestWithContext which is Go 1.13+.