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.

首先跟踪 NetPyNE-UI 如何加载和编辑群体参数，尤其是 popParams 中的 cellsList 字段。查看 issue #213 以及链接的 NetPyNEShowcase 示例，以了解该列表是仅被加载，还是也会在生成过程中使用。完成的标准是，用户可以在 UI 中查看和编辑细胞位置，并且对于导入的 NeuroML 模型，这些值仍然透明且可复现。

由索引模型根据 Issue 内容生成。