add a fix to distinguish between centred and edge grids when computing number of points over which we should loop and phasevols

also added a warning in the const_dt spacing function to catch the edge case where tmax or max_evolution_time are shorter than the first timestep, which would lead to an empty interpolation table

remove deprecated resolution setting

cleaned up some of the verbosity to be more like binary_grid and less annoying

updated the internal API for how grids are constructed to simplify the code

add option such that when resolution==0, the resolution is calculated automatically from the sample list.

add delete_grid_variable function

In my CEMP simulations, I use the above with something like this to zoom in around 0.8Msun in M1:

emp_population.update_grid_variable(
    name="lnm1",
    spacingfunc="gaussian_zoom(np.log(0.4),np.log(6.0),np.log(0.8),0.05,0.99,100)",
    resolution=0
)

Processed alot of what pylint suggested. Might change the naming conventions rules tho, the short parameter names are an issue, but lets not get too strict..

added some plots, restructured routine for scalingplots, fixing the phasevol part of the grid generator

played around with arg list. copied defaults from perl into defaults.py to include the physics defaults in the arg_string