Prevention of deletion of a ModelBuilder through a base class pointer

[ChristophJud]

I would recommend to add an empty nonvirtual and protected destructor to the ModelBuilder base class to prevent the deletion through a base class pointer.

ModelBuilder *m = PCAModelBuilder::Create();
delete m;

would only call the destructor of ModelBuilder but not the one of PCAModelBuilder. I think, it even leads to undefined behaviour.

Cheers