Test multicompartmental models with `neuron` module

[apdavison]

As a test of the adequacy of the connection/projection API, a test model that contains multi-compartmental neurons and multiple synaptic locations within the cells. An olfactory bulb model would be a particularly challenging example, as the bulb has both axo-dendritic and dendro-dendritic synapses

[apdavison]

Note that the neuron2 module is now called neuron

[apdavison]

see source:trunk/test/system/test_neuron.py

Can't yet handle multiple spike source locations in a single neuron, but that's an issue for another ticket.