remove nt from ModelParams, as there's not clear reason this needs to be known a priori
add functions to approximate the Eikonal equation

operate over the global domain (not fast marching)

methods for both 1 and 2 dimensions

generalizing to 3 dimensions will require 3d convolution
adjust smoothing windows for much better accuracy during reinitialization
front_velocity now works for multiple fronts

linear interpolation between

BUG: there is a bias in front propagation toward +x in the multiple front test
Merge branch 'master' of github.com:njwilson23/Iceberg.jl