Including a finite element option in the VACUUM code

One aspect of the VACUUM code\footnote{M.~S~.Chance, Phys. Plasmas \textbf{4} (6), June 1997.} is its legacy Fourier analysis in the poloidal variable, $\theta$, of the fields, which owed its origin to its compliance with the linear stability codes at PPPL. This may not be the optimum representation for modeling the modes currently observed in experimients and simulations. Furthermore, at present, for interfacing to the finite elements representation of say, M3D and M3D-C1, the inverse Fourier transform has to be taken to a discrete space. To alleviate these potentially numerical and representational problems, VACUUM is upgraded to include a finite elemnet option. These are piecewise constant functions in $\theta$. As in the Fourier method, care must be taken when addressing the singularities that is intrinsic to the Green's function technique that is used.