New functions

[tanmaybankar]

functions for cube visualisation, spike raster, spike count, storing feature vectors, connection weights

[balkaransingh9]

Hi Tanmay,
I think it would be better if you separate the new additions to another file. Perhaps we can have a new class and a set of functions which take in a reservoir object to make different types of visualizations. That would keep the code cleaner and more organized.