Move (most of) conode/ to onet/app

[nkcr]

At the moment we have to copy the entire conode/ folder in order to use a custom service. That would be great to keep only the minimal amount of code in conode/ and move the rest to onet/app.

Ideally we would only have conode/conode.go with the right needed static import for the custom service and the app.RunServer(config).