Consider adding a generic `Alias` type

[bruno-f-cruz]

This would allow a datastream to reference an already existing data stream elsewhere in the dataset. Some questions:

• Should likely be a Alias[TDataStream]
• Should not change the way data streams load lazily
• How should it load the target datastream if not loaded yet? Should it "force" initialization of intermediary streams that may be necessary?
• How should it be initiated/referenced?
• Should it be validated at construction time at all?
• Should not be able to reference itself