Discussions stub

A simple discussion model and controller stubs. I need it for view and for possible external service integration. For the time being it is attached, in the model, to a given FID (it could be either a district or a zone).

Later on we may add the spatial coordinates to a discussion so we may issue a spatial query to on PostGIS to see what discussion are about a given zone.
I know :smile:, maybe the question was not clear: should this field have default value for this field? It is in english, since we mostly will have polish users this can be misleading.