[WIP] Moving node validation from JL-Doctrine-DBAL to Jackalope

As suggested in the comments for this code in the doctrine-dbal implementation, this PR will aim to move the node validation to here.

The validate method currently also adds additional node operations (e.g. for node autocreate) to the transport, so I think it should probably be renamed / refactored.
is this from the git history|blame? while giving credit is fine, i think this is just too much. people who did a PR without adding themselves here probably do not mind still not showing up here. it should mention the main contributors if anything.