Calling services directly from nabd

[nmaggioni]

Some services, for example the weather monitor, already support being called from ASR or RFID/NFC.

It would be really nice if they could be invoked directly from nabd, much like the command/message packets already do for playing sounds and choreographies.

Since I am already using a raw nabd-MQTT bridge I though about injecting asr_event packets, but that's a really sketchy workaround and a generalized way of calling internal services could be useful for more straighforward integrations in the future.