ForEach doesn’t handle removals correctly

[MiaKoring]

It always removes the last view node instead of removing the one that actually got removed.
To fix this we need to know which node corresponds to which element.
I’m not sure if reordering is a problem too at the moment. It may be.

For Identifiables/with a given Identifier it should be easy to remove the correct ones.
Collections of non-Identifiables may need to be recomputed entirely.

I’m going to take a look at the correct-removal problem first.
There may be a reordering issue too, which I will test after.

[stackotter]

Yeah we need to require that elements are Identifiable. It’s been on my todos for a little while. Otherwise there’s no way to assign the child views sensible identities.