Extended ExportVTK to multigroup writing. Restructured Solveroutput for PN and MN Solvers to Multigroup with cleaner code. Removed dFlux as Screenoutput. Adapted other solvers to maintain compatibility with the new ExportVTK format. _solverOutput is now legacy and will be removed in future commits!

enabled multifield output for pn and mn solver. Unit tests not yet adapted!. PNSolver.solve still messy, needs cleanup!

MVP ML_MN solver stands. Weird mem leak in python. Newton an ML adaption not yet compatible. Huge r/w overhead in ML optimizer

removed commented code in MNSolver. renamed testgroup to validation tests. added scattering to MNSolver

fix #57 and #58. GLquad is now correct and tested for SphericalHarmonics. SphericalHarmonics normality unit test implemented. MN_Solver works (unvalidated) (solves #8). Changed tolarance for quadrature rules, due to weird behaviour of MC quadrature. Its now e-12 instead of e-15

added spherical gridpoints for MC and GL quadrature, prepared test cases. small changes to mnsolver. still does not work

added Option for Optimizer, added Optimizer, MNSolver compiles - not tested - base framework designed, added Entropy option and Entropy classes, added flux reconstruction step