Add support to Bridges without real interfaces

[trixpan]

Jouke,

Xen / KVM users frequently use Linux bridges (or OpenVSwitches) to support guest only network segments.

Current netctl configuration directives requires at least one interface added to "BindsToInterfaces". This creates a quite annoying situation where one mus either start its bridges manually (imho defeating the purpose of netctl) or to hack around the constraints by doing stuff like adding loopback or dummy interfaces into the BindsToInterfaces, etc.

It would be great if that could be simplified.

[joukewitteveen]

You can leave BindsToInterfaces out if you want. What is the problem?

[trixpan]

The problem is that I AM STUPID and have not tried that... Back to my cave