Improve loading of exam data

[Ghislain Hachey]

We often end up with exams data file loaded without the TESTID resulting in this. This looks like should never have been accepted by the loading process in the first place as it essentially an unknown exam. I think we need to enforce a few things when loading with TESTID being one of them.

So we need to clean these with care as the loading process loads data in the Exams table and a bunch of other related tables.

Then re-enforce the upload process a little to avoid at least errors that can not be cleaned up by simply reloading the exam file.

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