Ugly constat in QtNode

[mrusu]

In qtnode.cc there is a constant int QtNodes which holds the number of elements in QtInheritance. Considering that this constant is widely used and new operators are being added all the time, it is very inefficient and a usual source of runtime errors if it is off by 1. There is also no logging associated with it that would help to identify it as a cause in due time. I think it's time to change it to a more flexible approach.

[Dimitar Misev]

I submitted a patch.