Refs 31a61cbd

* deleted proxy models `APPassage` and `APScholium`
* removed namespacing for `related_names` (no more `mlgr_` prefix anymore)
* renamed Django application 'user' to 'meleager_user'

Inspired from #116 where Texts cannot have both a Passage and a Scholium.

New classes inherit from AbstractTextFromApi and use the same _texts reference.
It likely causes issues when Scholium IDs clash with Passage/Entity IDs.

Refs 774ce7ad