1470 reduce user tables querying

@Kartones CR this, please. Dashboard tables/visualization request does half database queries with this changes, and some of them are at model level, so some improvement should be transversal. Most of changes are for avoiding double computations, and I think they're safe, but maybe you see something I shouldn't do.
uff, careful with this one. I would remove it, the relator is already giving me lots of headaches because internally caches many of the "related objects", so caching it also will induce more sources of problems.