Add workflow version to classifications

Closes #254
I don't think we can trust clients to always send the correct workflow version back though, and how do we verify that a classification comes back with the correct workflow version? 

I don't really like either option. 

Weren't we going to lock the workflow once a project is 'live' anyway? Making changes to workflow text won't cause a new version of the workflow object to be created so people could still fix typos and spelling errors, but not change the actual requested tasks.