WIP Capability detection for networker

In a first approach the decision on using the standard or the safe networker has been done based on the provider type. In case of all but MAAS the safe networker has been used. Now a new environment capability has been added, so that each provider can return if it requires a safe networker for the current machine. As this today depends on the machine (local provider dislikes the changes done by the networker on the bootstap node, because it's the host system) and if the machine has been manually provisioned.

Fixes #1354365.
That's an open point yet. But would dislike to change the signatures during versioning. Changing also the names the `New...V0()` always create a V0 and `New...V1()` a V1 and so on. That directly matches and there's no need to change the calls you want to create the former version.