Introduce Nexus Channel Origin Command generation, as passthrough commands carried in 'full' protocol keycode messages.
These commands are used to create secure Nexus Channel 'links' between controller and accessory devices. For more information, see: https://nexus.angaza.com/channel. Corresponds with NEXUS_GLOBAL_VERSION == 3.1.0. Version moved to 3.x.y as interleaving origin commands breaks backwards compatibility with 2.x.y in the nexus-embedded repository.