Allow certain Neuralynx files to be excluded from being read as a part of neuralyxRawIO

[manimoh]

Hi,
First of all, thank you for developing this wonderful tool! I had a suggestion for a feature that I think can benefit the project:
The way NeuralynxIO or NeuralynxRawIO seems to work is that it goes into a folder and then reads all the NCS files present in it and stores it in a variable, unless that NCS file is empty (only has header). It would be great if we can have exclude flag in this 'folder' mode IO so that one can mention the NCS/NTT or other files that we don't want to be read for further processing steps like spike sorting (for instance). This reason could be that these particular NCS files may contain signals being sampled and or/filtered differently from the spike channels. For instance, maybe the user needs a real time LFP display (sampled at a typically lower rate) on the Neuralynx Acquisition software Cheetah, and Cheetah doesn't support changing signal properties only for display (It can only change the acquisition rate of that particular channel). This channel and its corresponding NCS file could also be representing some other physiological signal like EMG, or running speed of an animal from a separate encoder etc. And since we don't want these NCS files to be part of the spike sorting pipeline, we should be able to exclude them via neo itself rather than manually renaming the file extensions or putting the files in some other folder.

[JuliaSprenger]

With #1043 merged we can close this issue for now. #1038 is under review.