Use FSize when it is related to particles

Addons/CKernelApi/Src/CKernelApi.h

Addons/CKernelApi/Src/CScalfmmApi.h

Addons/CKernelApi/Src/FInterEngine.hpp

Addons/CKernelApi/Src/FScalfmmApiInit.cpp

Addons/CKernelApi/Src/FUserKernelEngine.hpp

Addons/CKernelApi/Src/ScalfmmCKernelApiCore.cpp

Addons/CKernelApi/Tests/testCKernelApi.c

Addons/CKernelApi/Tests/testChebInterface.c

Addons/CKernelApi/Tests/testUseNewApi.c

Addons/CKernelApi/Tests/testUserDefinedKernelApi.c

Addons/FmmApi/Src/ScalfmmApiCore.cpp

Addons/FmmApi/Src/ScalfmmApiRotation.cpp

Addons/FmmApi/Tests/testFmmApi.cpp

Examples/ChebyshevInterpolationFMM.cpp

Examples/ChebyshevInterpolationMPIFMM.cpp

Examples/DirectComputation.cpp

Examples/LagrangeInterpolationFMM.cpp

Examples/RotationFMM.cpp

Examples/RotationMPIFMM.cpp

Examples/changeFmaFormat.cpp