We need to add versioning to The pluggable interfaces. Versions should be logged and exposed via a meta query interces to allow clients to understand the level of support associated with particular formats.

Open question: should the version be assoicated with a scheme (i.e. all pluggables associated with a scheme--e.g. both, evidence and endorsement handlers) share a version (in the same way they share the scheme name), is each interface versioned separately?