JoinConditions inside container and connector conditions

[FrancoLiberali]

orm.And(), orm.Or() and orm.Not() only support WhereConditions inside, making it imposible to do
orm.Or(
attribute = "something",
relation.attribute == "something",
)

In order to do that, the join must be transformed in a EXISTS.
Once done, WhereCondition can be deleted and orm.NewQuery will not need to put the model as generic type.
It means also changing the way preloads are done, because we can not do a preload from a EXISTS. Maybe the preloads should be done on JoinConditions and not with methods of the condition model