Introduce Nokee repository overrides

[lacasseio]

trafficstars

For air-gapped or firewalled network, we need overrides to select different URLs. Something like dev.nokee.repository.release.url.override and dev.nokee.repository.snapshot.url.override could work.

We could also use dev.nokee.repository.url.override to override both repos, however, I'm unsure it would be considered best practice.