Interactive setting of LS, SL, act_perm
Interactive setting of LS, SL, act_perm

Using time_dependence: a dictionary to override the initial lattice
spacing, sarcomere length, and actin permissiveness at each  timestep.
Valid keys are "lattice_spacing", "z_line", and "actin_permissiveness".
Each key may contain a list of the values, to be iterated over as
timesteps proceed. The first entry in these lists will override passed
initial values.

cdw/multifil