NeuroML jupyter notebook (Issue #20)

[irahulsonkar]

This version of notebook (notebook_NML.ipynb) loads NeuroML model in Juptyer and gives user option to edit and run through interactive widgets.

• it seems to work fine with HH model.
• it read and edit (regex search) nml files for required changes through widgets.
• network file is update with second pulse as zero amplitude since notebook uses only single pulse.
• new output file creation has been added to LEMS case file for plotting results in notebook after execution.
• a more generic version of this is under development which shall load any NeuroML model.

[pgleeson]

Thanks @irahulsonkar. Will test and then merge to master