The policy about how to create slots was not completly clear.
Now, only add *pointers* or *references* to class attributes,
never do a "copy by value". Reflect that change in SlotTemplate<>
various partial specializations.
Hammer in your head that in C++ functions templates do not allow
for partial specialization. So write only *one* template for
::getSlot<>() (refdefinition simply got ignoreds, at least with gcc).
* Bug: In Slot, only one template for getSlot<> (see above).
Adjust SlotTemplates<> to provides partial specialization only for:
* "const Data&".
* "Data*".
* "const Data*".
* "Data* const"
* "Record*".
* Bug: In Instance::_getRecord(), suppress slot based on transient
values "XCenter" & "YCenter".
* Bug: In CRL::ToolEngine::_getRecord(), suppress slot "Name" based
on a transient value.
* Change: In ::getRecord(std::list<Elementt>*) (and variant), pass
all elements to ::getSlot() as (const Element*).
3b5a0f5bd2