_sum is only allowed in one design document, split up
Don't allow negative values, support average of course value
Back to only one design document, one view returning all data

The view returns the following array:
[<maximum value of session>, <user results>, <num user answers>]

However, when a user's individual results are needed, the session
maximum is not available. As a result, two queries are needed.
On the other hand, we usually want to show results for 'me' as
well as for the whole session at the same time, so we can return
both results on the server side.
Implemented question type and abstention filter
Split up learning progress calculation to several views

This had to be done because our CouchDB version is too old, and
it does not support the features required to do this in one view.
Well, don't forget to add the files...
Fixed problem with empty possible answers
Add view to find all sessions identified by a list of course ids
Add view for database authentication