Instructions for running models from NMC portal

[pramodk]

Recently we have updated NEURON-CoreNEURON usage workflow in #374 (see README).

The NMC portal provides various cell models. As part of this ticket, we should document instructions to run these cell models using NEURON and CoreNEURON.

From initial testing few months ago, I remember following changes:

• [ ] Update synapse model for Random123 : ProbAMPANMDA_EMS.mod ProbGABAAB_EMS.mod
• [ ] Update run.py for CoreNEURON

    print('Running for %f ms' % neuron.h.tstop)
    #neuron.h.run()
    from neuron import coreneuron
    coreneuron.enable = True
    neuron.h.cvode.cache_efficient(1)
    neuron.h.stdinit()
    pc = neuron.h.ParallelContext()
    pc.psolve(neuron.h.tstop)

• [ ] Update voltage recordings API usage (see https://github.com/neuronsimulator/nrn/issues/718)
• [ ] Integration of NMODL and testing (linked to #344)