Added the following neuron classes as subclasses of 'ciliated neuron':
PVR
CEM
HOA
HOB
PCA
ray neuron type A
ray neuron type B
SPD
SPV
I debated (to myself) whether to just add 'HO neuron' and 'ray neuron' to the 'ciliated neuron' class as it seems HOA and HOB are all of the HO neurons and 'ray neuron type A' and 'ray neuron type B' are all of the ray neurons. I can do that instead if we prefer.
Takes care of issue #9
Added the following neuron classes as subclasses of 'ciliated neuron':
PVR CEM HOA HOB PCA ray neuron type A ray neuron type B SPD SPV
I debated (to myself) whether to just add 'HO neuron' and 'ray neuron' to the 'ciliated neuron' class as it seems HOA and HOB are all of the HO neurons and 'ray neuron type A' and 'ray neuron type B' are all of the ray neurons. I can do that instead if we prefer.