Store Ensemble version number in topology node and verify ops

Ensemble will occasionally have backwards breaking changes. To accommodate this scenario, store a version number in the topology node at bootstrap. This version number is a monotonically increasing integer and is in part of the Ensemble package itself.

Any topology operations will raise a suitable error about working with too old a version when they parse the topology node. This should result in the desired outcome of failing early without requiring additional checking against ZK. There may be better ways to do this.