Baseline cube scene various fixes

[przet]

From PR #91 :

1. Fix the rotation logic to inspect the top/bottom faces without needing to go around a full circle (as we then cover faces we already have seen).

2. At least on the middle cube, there is a model matrix reset issue (evident in the snapping to a different face).

3. If I am working on 1 and 2, it would be good to also reorder the slots in a more logical fashion (the third slot is the middle cube)