Added Dictionary store to ElementList
Fixed iterating Elements with stub/deferred values
Fixed destubbed Elements not being added to Datamodel's ElementList
Optimised destubbing: stub Elements are now converted into full Elements (instead of being replaced)
OnStubRequest will now import the returned Element if necessary
Fixed an Element.Owner being set before Element.ID
Moved all Element validation to ElementList.Add
Fixed KeyValues2 decode
Fixed KeyValues2 sometimes writing the root element twice
Fixed writing strings containing quotes in KeyValues2