changes in HH_cond_exp.py to make it work with mock. Minor changes on run_all_exaples.sh
example varying_poisson.py is now working with mock. It required a modifiction in the mock/populations.py file, in the _set_parameters function, in which I set simplify to False in parameter_space.evaluate(simplify=False). There is still a RunTimeError of a divide by zero in a lazy array, but that I cannot reproduce with pdb
minor changes in run_all_examples.sh. Now, all examples run under nest, mock and neuron without errors, except for nineml_neuron.py, as the nineml binding is not functional