Move to a relative diff in M2L based on array index.

Src/Components/FAbstractKernels.hpp

Src/Components/FBasicKernels.hpp

Src/Components/FTestKernels.hpp

Src/Components/FTestPeriodicKernels.hpp

Src/Containers/FOctree.hpp

Src/Core/FFmmAlgorithm.hpp

Src/Core/FFmmAlgorithmPeriodic.hpp

Src/Core/FFmmAlgorithmTask.hpp

Src/Core/FFmmAlgorithmThread.hpp

Src/Core/FFmmAlgorithmThreadProc.hpp

Src/Core/FFmmAlgorithmThreadProcPeriodic.hpp

Src/Core/FFmmAlgorithmThreadTsm.hpp

Src/Core/FFmmAlgorithmTsm.hpp

Src/Kernels/FAbstractSphericalKernel.hpp

Src/Kernels/FSphericalBlasKernel.hpp

Src/Kernels/FSphericalBlockBlasKernel.hpp

Src/Utils/FMath.hpp

Tests/testStatsTree.cpp