Pitfalls remarks

[coolya]

I think cases 3 and 4 in the broken references section are not entirely valid under all cases

https://github.com/coolya/maintainable-generators/blob/master/docs/Pitfalls.md#broken-references

I think 3 only happens when it is replaced with a totally different node and hence the reference pointing to it would become invalid because it violates the reference constrains. At least when running a .replace with operation from within MPS all references are pointing to it correctly afterwards.

For 4 I'm totally unsure ... I was not able to observe this behaviour, in fact I think some mbeddr generators heavily rely on this. Though I would argue that it is a anti pattern to have generator that reduces something and does not have rules to do something with the referencing concepts. Usually these are tightly coupled and if the reduction happens during the same generation phase this should not be an issue.

I thinks the mapping labels section shouldn't sound that concerning. I sound a bit to negative to me.