Refactor device-init to not use sub-commands any more

[Govinda-Fichtner]

It turns out that device-inits main use case is to do stuff automatically at boot of a device.

Having commands that also allow to show the current individual settings make sense (if at all) just for a limited set of settings. Thus it would be consequent to just get rid of all of them.

Let's have only one command that sets different things at boot.
This gives device-init more focus and simplifies its architecture.