Add option for display/editing of cell list

Specifying a list of cell positions is a standard feature of NetPyNE populations, and will be crucial for loading/displaying NeuroML models, where the positions are generated in NeuroML (e.g. with pyNeuroML or NeuroMLlite) and exported to NetPyNE using "cellsList" in the popParams element, e.g. https://github.com/OpenSourceBrain/NetPyNEShowcase/blob/0fa6c7032d9b2984f169d48773e573e16b9a8505/NetPyNE/UI/HHCellNetwork.txt.json#L99.

However this is not curently supported by the UI. The cellList etc. is probably loaded in the background by netpyne core, and possibly used for generation (although possibly not, see https://github.com/MetaCell/NetPyNE-UI/issues/213), but the user can't see this. Adding this feature in the UI will make NML imported models (and an other models that use cellList) more transparent & reproducible.

Comece rastreando como o NetPyNE-UI carrega e edita os parâmetros de população, especialmente o campo cellsList em popParams. Revise a issue #213 e o exemplo vinculado do NetPyNEShowcase para entender se a lista é apenas carregada ou também usada durante a geração. A tarefa estará concluída quando os usuários puderem ver e editar as posições das células na UI e os valores permanecerem transparentes e reproduzíveis para modelos NeuroML importados.