Support for ifroute

bnc#897394, bnc#866250
> > `@Routes += dev_routes`
> 
> better to use `<<` as this call makes copy of array so for some s390 beast with a lot of network devices it can be slow

@jreidinger maybe I am missing something  but I don't see how `arr1 += arr2` can be replaced by `<<`. Using simply `arr1 << arr2` is wrong because it embeds the second array instead of appending it. (Caught by tests, yay @mchf ). I will use `arr1.push(* arr2)`.