Simplify the code of the dccd

[vicb]

We use DuplicateMaps in order to track linked and unlinked elements of collection.

DuplicateMap.put has an insertBefore argument.

However this argument is never used, removing it would allow simplifying the code.

Could we safely drop it ?

/cc @mhevery

[mhevery]

If we don't use it, and if tests pass after you remove it, then it must have gotten there organically, and it should be removed.

[vicb]

Tests do pass, I'll take care of that