interpose-neuroml.py: Translate points by the backbone curve

IOW wind the neuron positions around imaged worm's backbone.
interpose-neuroml.py: Reduce unrealistically large radiuses to 1/10
interpose-neuroml.py: Show poseinfo string in the title of the plot figure
interpose-neuroml.py: Support y-axis shift in poseinfo
interpose-neuroml.py: Support view angle tilt in poseinfo
interpose-neuroml.py: Offload load_neuron() and loop (load_neurons() now) to nmllib.py
nmllib: Print progress on stderr
neuroml-soma-to-json.py: Export NeuroML2 data to JSON for nemashow
bblib -> poselib, clean up function names
Move coordinate projection / translation by bb from interpose-neuroml to poselib
nmllib.load_neurons(): Support loading from previously exported json data as well (much faster and more convenient)