Change node not disabled when the same change node was applied elsewhere

[amchiclet]

When a tree has two same change node on a different path, applying one of them should disable both. See picture.

[amchiclet]

See commit comments. This is not entirely fixed. The nodes are correctly disabled, but if the same changes are not visible when a change is applied, it will not be grayed.

[reprogrammer]

I reviewed your commits for this issue. I think the problem is that the code looks for related changes only when a change is applied. However, the relation between changes is commutative. That is, if c1 is related to c2, c2 is also related to c1. When the user expands a node, we should check if any of its related changes have been applied. I think the hook to the expansion action is the getChildren method. We should add a search in the getChildren method to see if any of the children changes are related to an applied change.