Additional KS_Solver/PPCG added
the PPCG solver has been implemented at Gamma and k. all example have been run with diagonalization='ppcg' with successful results. It is not faster that davidson but involve diagonalization of smaller matrices.
the PPCG solver has been implemented at Gamma and k. all example have been run with diagonalization='ppcg' with successful results. It is not faster that davidson but involve diagonalization of smaller matrices.