Remove SCORM dependancies

Relates to https://github.com/adlnet/xAPI-Spec/issues/501

This PR is **not ready to be merged** and is a work in progress. That said, I am trying to keep this in a state where it could be merged as an improvement after each commit by commenting out unfinished bit. I also appreciate comments on the general direction and specific changes so far.  

It may be that I get to a certain point with this and then put it on the back burner to focus on other, more quick-win, issues. In that event, it'd be worth merging to avoid conflicts. 
This either needs to be a SHOULD or a SHOULD NOT. I'm in favour of SHOULD NOT because aside from backwards compatibility, I don't see a need to enforce these.