Global configuration always present in new-traefik.yml/toml

[vegasbrianc]

In the https://github.com/containous/traefik-migration-tool/blob/master/static/configuration.go#L27 file it creates the Global configuration section in the new-traefik.yml/toml regardless if content is being imported or not.

An empty Global Configuraton entry in the yml/toml results in Traefik not being able to start.