Adding gradient, divergence, and diffusion (P2) operators with IcoShellMap blending.

operators.toml

operators/diffusion/CMakeLists.txt

...s/diffusion/P2ElementwiseDiffusionIcosahedralShellMap.cpp

...s/diffusion/P2ElementwiseDiffusionIcosahedralShellMap.hpp

...lementwiseDiffusionIcosahedralShellMap_apply_macro_3D.cpp

...hellMap_computeInverseDiagonalOperatorValues_macro_3D.cpp

...lementwiseDiffusionIcosahedralShellMap_apply_macro_3D.cpp

...hellMap_computeInverseDiagonalOperatorValues_macro_3D.cpp

...entwiseDiffusionIcosahedralShellMap_toMatrix_macro_3D.cpp

operators/divergence/CMakeLists.txt

...ce/P2ToP1ElementwiseDivergenceIcosahedralShellMap_0_0.cpp

...ce/P2ToP1ElementwiseDivergenceIcosahedralShellMap_0_0.hpp

...ce/P2ToP1ElementwiseDivergenceIcosahedralShellMap_0_1.cpp

...ce/P2ToP1ElementwiseDivergenceIcosahedralShellMap_0_1.hpp

...ce/P2ToP1ElementwiseDivergenceIcosahedralShellMap_0_2.cpp

...ce/P2ToP1ElementwiseDivergenceIcosahedralShellMap_0_2.hpp

...twiseDivergenceIcosahedralShellMap_0_0_apply_macro_3D.cpp

...twiseDivergenceIcosahedralShellMap_0_1_apply_macro_3D.cpp

...twiseDivergenceIcosahedralShellMap_0_2_apply_macro_3D.cpp

...twiseDivergenceIcosahedralShellMap_0_0_apply_macro_3D.cpp