Calculate tentative mark from updated WAM

[tarantoj]

Like most, I check my WAM incessantly to be able to figure out how I might've performed on a subject, why not extend this to do it for you?

I was thinking of creating a simple pull request to implement this, but it looks like it might be best to implement it as an extension of the rich results feature.

In the meantime, I think I might write a simple bolt on to the master branch to achieve this. The only real problem I think might arise is the potential of more than one subject updating at the same time, and how to deal with accounting for that when there are multiple WAM updates.