Support multiple schema file versions

[vohmar]

Currently registry supports only one schema file version at a time - this is a problem once we need to update a schema versions creating a situation where registry and all the registrars would need to update at the same time, otherwise the requests would start failing.

In most cases the changes in the schema versions are minor so temporarily supporting multiple versions should generally not be a problem.

so i would suggest to check the schema file / path validity against the schema repo ie https://epp.tld.ee/schema/ and if the version is there then give the request a green light?