In memory configuration and plugin

[saschagrunert]

I'm not sure if this is a great idea so I want to put it under discussion: What about providing a default bridged network fallback if no further configuration was found? We would have to built-in the configuration as well as the binary code of the plugin here. I imagine that this could be a strong default if users want to try out podman without having all the CNI plugins and configs at hand.