Revert "Revert "Merge remote-tracking branch 'origin/FD_solver'""

src/CMakeLists.txt

src/DCPSE/DCPSE_op/DCPSE_Solver.cuh

src/DCPSE/DCPSE_op/DCPSE_Solver.hpp

src/DCPSE/DCPSE_op/DCPSE_op.hpp

src/DCPSE/DCPSE_op/DCPSE_surface_op.hpp

src/DCPSE/DCPSE_op/EqnsStruct.hpp

src/DCPSE/DCPSE_op/tests/DCPSE_op_Solver_test.cpp

src/DCPSE/DCPSE_op/tests/DCPSE_op_Solver_test.cu

src/DCPSE/DCPSE_op/tests/DCPSE_op_Surface_tests.cpp

src/DCPSE/DCPSE_op/tests/DCPSE_op_subset_test.cu

src/DCPSE/DCPSE_op/tests/DCPSE_op_test3d.cpp

src/DCPSE/DCPSE_op/tests/DCPSE_op_test_base_tests.cpp

src/DCPSE/Dcpse.cuh

src/DCPSE/Dcpse.hpp

src/DCPSE/DcpseDiagonalScalingMatrix.hpp

src/DCPSE/DcpseInterpolation.hpp

src/DCPSE/Monomial.cuh

src/DCPSE/Monomial.hpp

src/DCPSE/MonomialBasis.hpp

src/DCPSE/Support.hpp