Fix to support larger datasets

[nenikola]

Previous approach with recursive call to getFlattenedTree and getFlattenedTreePaths was prone to "Maximum call stack sizeexceeded" error or slow rendering (couple of minutes). Changed it to iterative approach to avoid such behaviour.

Couple of times I encountered a maximum argument size issue (explained here ) caused by Array.splice so I've moved it out in favor of this not as pretty but effective solution.