better use of local indices

[jnsbck]

(1) the function index_of_loc returns the highest index for the closest segment and the lowest for the furthest, see #30 and (2) it is multiplying with branch_ind because we had to rely on global compartment indices -- now this could be solved with local indices and then it is not necessary anymore to pass a branch_ind to the function

jaxley/jaxley/utils/cell_utils.py

Line 161 in 729c1ca

return branch_ind * nseg + ind_along_branch

Originally posted by @lappalainenj in #277 (comment)

Also see here

[michaeldeistler]

Can this be closed @jnsbck ?

[jnsbck]

Should be adressed by #447.