Add mixed k_mass operators

operators-k_mass.toml

operators/k_mass/CMakeLists.txt

...tors/k_mass/P1ToP2ElementwiseKMassIcosahedralShellMap.cpp

...tors/k_mass/P1ToP2ElementwiseKMassIcosahedralShellMap.hpp

...1ToP2ElementwiseKMassP1CoefficientIcosahedralShellMap.cpp

...1ToP2ElementwiseKMassP1CoefficientIcosahedralShellMap.hpp

...ly_P1ToP2ElementwiseKMassIcosahedralShellMap_macro_3D.cpp

...entwiseKMassP1CoefficientIcosahedralShellMap_macro_3D.cpp

...ly_P1ToP2ElementwiseKMassIcosahedralShellMap_macro_3D.cpp

...ix_P1ToP2ElementwiseKMassIcosahedralShellMap_macro_3D.cpp

...entwiseKMassP1CoefficientIcosahedralShellMap_macro_3D.cpp

...entwiseKMassP1CoefficientIcosahedralShellMap_macro_3D.cpp