Neo & MNE compatibility with Nix

With nixworks EEG data can be represented in Nix via the MNE package. This includes Brainvision (vhdr) as well as EDR files. Both of these formats are also supported to some extend by the Neo library ([BrainvisionIO](https://github.com/NeuralEnsemble/python-neo/blob/master/neo/io/brainvisionio.py) and potentially [AxonIO](https://github.com/NeuralEnsemble/python-neo/pull/738#issuecomment-623443768) or [WinEDRIO](https://github.com/NeuralEnsemble/python-neo/blob/master/neo/rawio/winedrrawio.py)), which also has an interface to the Nix format via the [NixIO](https://github.com/NeuralEnsemble/python-neo/blob/master/neo/io/nixio.py).
For me there are two interesting aspects here:
1. For the implemented formats, are the Nix files generated via MNE and Neo compatible, ie. can they be read by the respective other program?
1. Is there a general guideline on how data in nix should be organised such that the Nix format could be in general used as an intermediate between MNE and Neo?