Store framework version in events

[drewmccormack]

We currently store the model hashes with events, so we can identify models that are unknown and pull out of a merge.

It would be good to also have major framework versions. If changes are made to the framework that could confuse older versions of the framework, we could bump this version.

Each event would record the framework version, and if a version is found that is newer than the current framework, an error arises.