In order to constrain the central slope we find all the elements connected to the central vertex. The slope will be approximated over these using the finite difference method
The NewtonSolver has been subclassed to try to auto enforce the zero boundary central condition by modifying the residual vector and the gradient matrix. This is a work in progress
BREAKING CHANGE:
the polytrope module will be used as an initial guess to the solver. A skeleton of this has been imported from https://github.com/tboudreaux/FEMPolytrope
This module will need major updates still to handle 3D, proper boundary conditions, and to incorporate it with the rest of our meshing scheme