Big commit: compartment mapping + label improvements

1) Fully labeled contextual voltage plots (in ms)
2) Axial current label fixed
3) Diameter relabeled
4) Compartment mapping function implemented. The function will convert
A to B number of compartments, where A and B can be any positive
integer, as long as A>B. The attached video shows mapping to 10
compartments from 22.
5) Colormap now based on range from -80 to +20 mV
6) Function call now takes arguments (Filename, StartTime, EndTime)