Support changeset replication state.yaml

[datendelphin]

Changeset replication at https://planet.osm.org/replication/changesets/ has an odd state.yaml file.
pyosmium-get-changes looks for state.txt, can't find it and errors out with ERROR: Cannot read state file from server. Is the URL correct?

[joto]

Changeset replication is something totally different. This isn't supported by pyosmium-get-changes or any of the other tools.

[lonvia]

The issue is more of a reminder to look into changeset replication and how much work if would be to support it. Not very high priority but also not completely out of scope for pyosmium.