sys: net: Initial import of a simple data-forwarding MAC protocol (nomac)

This is basically an adapter translating `netapi` IPC calls into `netdev` function calls.

Depends on ~~#1448~~ (merged) and ~~#2027~~ (merged)
Okay, thanks for the clarification! Then this approach is perfectly correct :)
I just misinterpreted the sequence of events (this means that the current CC110x driver will need a PR).