Refine the way we add Generic Elements

[Castone22]

Currently there's room for confusion with the way the generic elements get created that @greenarrowdb raised.

I think i'm going to add a add_generic_element method that defaults to a CoreElement for creating elements that are meant to be used as parents or base elements for location.

I'll probably add a warning to add_element if it's called without an element type the first time the code point is hit per page (as as not to log spam)